Rather than critiquing the gaming performance and digging deep into the specs of the Corsair M65 RGB Pro, the focus here will be to inform others as to how well i personally like this mouse and its usability and compatibility with a Linux based OS.
the TL:DR version
Unless you're willing to break out the soldering iron, stay the hell away from this mouse! Corsair is using horrible, poor quality micro-Omron 50m switches for both the primary and secondary buttons and they fail very quickly according to many people, including myself. I would suggest avoiding any mouse using Omron "50 million click" switches.
intro
My Cooler Master Inferno finally gave up the ghost after 11 years. It started clicking the primary button by itself and although i might have been able to resolve the issue, i've had it apart several times to clean crap from the wheel sensor, chipping the case in the process, and its feet were just about worn down to the nub. Oh, and all that nice rubberized coating was worn off and it didn't take long for that to happen either. Time for a new rodent.
The Corsair M65 RGB Elite is a wired, right-handed, 7 button (plus the scroll wheel and its button) gaming mouse with solid specs, like a very accurate 18,000 DPI optical sensor which provides a max resolution that's an order of magnitude higher than any human could ever manage, but bigger numbers are more impressive apparently. With the KDE desktop and the mouse sensitivity set to 50% and acceleration enabled, the M65 is set at around 600 DPI for a 17 in. 1080p laptop display.
looks and feels
I think the M65 is a very nice looking mouse. I'm not entirely sure if it looks more like a weapon or a mouse with its somewhat prominent red 'sniper' button and vented aluminum frame, but i do like its angular yet smooth looks. The one piece top seems to be made of silicone and it feels velvety smooth. The plastic, concave sides have a hard, sandpaper-like texture which, as i suspected it would, is already wearing smooth after only several weeks of daily use.
The M65 feels good in the hand, but it's not as ergonomic as my Inferno was and because of the way the sides are shaped it's a little harder to lift off the pad, even with the rough textured sides and even though all the rubbery coating was worn off of my Inferno. I removed all the weights to make the mouse lighter and although this surely made a difference, it wasn't one i could readily feel. It also feels narrower between my thumb and pinky fingers, yet it's actually a little wider in that area compared to the Inferno. The M65 is a shorter mouse designed to be 'claw' or 'fingertip' gripped and this is certainly my preferred style of holding a mouse.
As implied, the M65 has three removable weights, each located in a different spot, however the way this feature was implemented wasn't well thought out. The weights are held in place with screws and replacing a screws after removing a weight is a little tricky because the hole in the weight guides the screw into it's threaded socket, though one could just leave the screws out entirely for more of a weight reduction. Had the engineers had their thinking caps on, they might have used these screws to hold the mouse together as well instead of adding two more which, to their credit, at least aren't located under the damned mouse feet, thus disassembly is very easy requiring only a Phillips driver. Although on the smaller side this mouse is quite heavy, even with the weights removed. It also has a very solid feel thanks to the rigidity of an aluminum frame and there's no detectable rattles when shaking it or squeaks when squeezing it.
Like many wired gaming mice, the M65 uses a braided cord which i find to be a gimmick. These cords are often rather stiff and unlike the older rubber/plastic/silicone sheathed cords, the slight noise that the nylon braiding might make as it drags across a rough textured mouse pad could be annoying to some, though this can be managed with some creativity.
The primary and secondary buttons, both rated at 50 million clicks, are significantly quieter and lighter feeling than those of most mice and while i personally don't like loud buttons, these are so quiet that there's hardly any audible feedback and so sensitive that i couldn't rest my fingers on the buttons without clicking them. Whereas with the Inferno i knew i had clicked something because of the audio and tactile feedback, i now find myself looking at the display for confirmation. If we were to compare the feel of these buttons with the trigger of a gun, the words 'hair trigger' would certainly be appropriate. The throw of the buttons -- how far they move before a click is registered -- is much less than with the Inferno and i'm fine with that part of it.
Overall the click of the right and left buttons just doesn't feel good with the right button feeling slightly crisper than the left, possibly because its switch is positioned slightly differently in relationship to the button than the one for the left button. Several times i had the mouse apart to see if anything could be done to increase the pressure required to click the primary and secondary buttons and though that was easy enough to do with some strategically placed foam tape, nothing solved the problem of the extremely mushy feel of the buttons.
Getting back to the buttons again because this is such a negative aspect of this mouse, Corsair is using the Omron 50m switches for the primary and secondary buttons and though they are rated at 50 million clicks, they are absolute garbage and apparently quite a few gaming mice use these switches. Mine lasted a few weeks before developing what i might call 'switch chatter' and clicks not registering. Besides the laughably short lifespan of these switches, they are so sensitive that i couldn't rest my fingers on them and so mushy that you actually end up pressing the buttons much harder in order to make sure the click registered. These attributes actually make the mouse more fatiguing to use. I ended up replacing both the primary and secondary buttons with a pair of Huano Blue Shell Pink Dot switches.
The down-click of the wheel button is significantly stiffer and crisper than that of the primary and secondary buttons, leaving me with no complaints here. One thing i very much disliked with the Inferno was the barely noticeable notches of the wheel when scrolling and the M65 is slightly better in this regard, though still lacking. The wheel is nearly completely silent which i much prefer over one that sounds like a ratchet wrench. As with many mice, one can scroll the wheel a half notch and it will stay there instead of rotating to the nearest detente in the wheel. Unfortunately there is no side scroll function, though pushing the wheel to the right results in a middle click because the switch is located on the right side of the wheel shaft.
The M65 has three buttons on its left side and, thankfully, none are of the 50m type. The 'sniper' button requires more effort to press than any of the others and this is fine given that the thumb rests on it. The back and forward buttons are narrow in height but still quite usable.
The last two buttons behind the scroll wheel control sensitivity by default and they require more pressure to operate than is necessary, though i'm not complaining. Their location is good, making them candidates for binding to other functions for game use.
Missing from the M65 are the 'wing' buttons of the Inferno which were located on the outside edges of the primary and secondary buttons. In my opinion these were great buttons to have and there's no reason to not have them on all gaming mice since they don't interfere with any other operation as long as they're placed smartly.
configuration
The M65 will of course work as a standard 5 button mouse on Linux without any additional software, however when i first plugged it in, it defaulted to a 'breathing' mode where the LEDs slowly changed colors. I find this to be really annoying and Corsair's ultra-bloated, ultra-buggy and Windows-only iCUE crapware is needed to configure the RGB lighting, DPI and button assignments since they don't do Linux. I grabbed a Windows 8 image and installed it in a VM in order to be able to use their shitty software and the process was about as frustrating as it could possibly be. Many times it refused to write to the internal memory of the mouse or froze the OS. Changing something as simple as the USB report rate caused all of the settings in that section of the GUI to become disabled. Sometimes re-plugging the mouse worked, other times a soft reset did the trick. The latter is accomplished by unplugging the mouse, holding down both the primary and secondary buttons and plugging the mouse back in while continuing to hold the buttons down for about 15 seconds or so. After a while the mouse seems to reboot and all settings should be at their defaults.
You can also access the firmware file directly which might of been helpful were i able to download different versions to try but Corsair doesn't make them available. To boot the mouse in this mode, unplug it and unscrew the upper-right weight retaining screw. In the hole where the weight goes is another smaller hole with a button in it that you can press with something small like a toothpick. If you press that button while plugging the USB connector back in, the mouse boots in something like USB storage mode and you can open a file manager and see the new device/folder inside of which is a firmware.bin file. Apparently you can replace it with another version and, i presume, reboot the mouse again by re-plugging it.
While there is a Linux configuration utility for the M65, the ckb-next software means having to run a daemon in the background since, at the time of this writing, they haven't yet reverse engineered the communication protocol that Corsair is using to talk to the device and so you can't store any settings on the mouses internal memory. Also i was warned about a stability issue when i installed it on Manjaro. Using the utility, any button can be assigned to any other button, macro, or keyboard key, or it can be used to invoke a program and, unlike Corsair's iCUE crapware, you can also adjust the lift-off distance with ckb-next. Honestly it would be a great utility were it able to write to the mouses internal storage.
If you don't want to use any 3rd party software to configure the mouse, there is yet another potential option for Linux by using Xorg configuration files, though there appears to be limitations.
conclusion
I'm quite sure some people will not like the way the primary and secondary buttons work since the throw is very short, they require very little pressure to operate and they are very quiet. If you're wanting a satisfying tactile feel when you actuate these buttons, look elsewhere. On the other hand, these characteristics may be a plus for some, especially if working or gaming in the vicinity of those trying to sleep, however the atrociously short lifespan of the Omron 50m micro-switches used for the primary and secondary buttons makes buying this mouse a fantastically poor decision in my opinion. Unless you're willing to replace the switches for the primary and secondary buttons, i would readily suggest staying away from this mouse, and Corsair products in general since they are not Linux-friendly, as well as any mouse/device that is using the Omron 50 million click switches.