I have one. Seems to holding up good. My homemade mount isn't doing so hot though. Usually I can't watch the RPMs with my build because it revs so fast. However, if I am cruising down a road and holding it pretty constant throttle I can look down and see it.
I use it more for coolant temp, air temp, speed, and distance.
i've had my vapor for one riding season. i can see it very clear. i have the dash and the x bars, so it's a really clean set up. speedo is spot on. i agree with maxtrax, i use mine for the speedo, coolant, distance, etc. I don't pay too much attention to the RPM's, but as far as I can tell they aren't jumpy. All in all, i think you'd like it
my 700 obviously has diff indicator lights than your 660, but as you can see since i have the dash, it kept my key in the same location and everything. i would imagine they have a 660 dash for the stock bars ?