just throw bags of cash at a senior driver developer from logitech or steelseries and see if you guys can land one:D i'm sure you guys are aware ALL of the reviews on ALL sites have been "build quality is great, best feeling mouse ever produced, too bad the software doesn't work....." i was SOOOO looking forward to the M90 and now I'm "unable" to buy it because EVERY SINGLE REVIEW said the driver is crap
so as it stands, i'm likely going with either a G600 or a G700 from logitech.... maybe when M91 comes out, the drivers would not be an issue
just as a product suggestion if you guys are going to design a "M91". the top (dpi up and down buttons) can you guys maybe consider making it contoured much like the G700 so it's easier to press and require shorter finger travel to reach them? also mirror those buttons on the right side of the mouse as well so you can use the middle finger to access additional buttons. additionally 2 ring finger button (situated slightly behind where your ring finger would normally sit to manipulate the mouse) so you have a ring finger top and ring finger bottom buttons) would complete the overall package.
as for the thumb side of the mouse, i think you can eliminate the 2 buttons way in the back.(instead, i would split the button directly behind the thumb into 2 buttons instead of 1 big button) those 2 button on the back are hard to reach during gaming anyway and from an ergonomics point of view, those buttons would be much better served when allocated to either the ring finger or the 2 dpi buttons on the right click side of the mouse. with those design changes, I doubt there would ever be a better ergonomically designed mouse then the "M91"?
(unless you guys figured out a way to go wireless w/o eating a battery every 8 hours