.86 would have been great if it didn't reboot all the time. I liked the improvements in the camera speed and typing. My problem is that every day I had to do 1-2 battery pulls to keep it alive. Otherwise, it locks the backlight on and the application switcher stops working. It will do that until the battery dies unless you force a reboot.
In my opinion, .86 is crap and should not be used.
Of course, the locking up stuff could just be unique to my hardware and that OS... although I've seen it reported many times that others have that issue too.
.75 was very very reliable for me, just a tad slow. Upgraded to .85, and although its a little more buggy there are no real issues and the speed at which the phone responds is phenomenal, much faster than .75.
.86 is like a plague. .75 was ok, but too many random reboots, and the ringer although on vibrate issue was terrible. .85, was faster, but removed bluetooth with videos, but had less reboots for me.
