There is some serious serious shite coming in 3.1, some good, some bad, some 'Wtf?'.
Would be a good idea for folks to take the time to eyeball now.
http://www.wowinsider.com/guide-to-patch-3-1/ There are major class changes, some of which change mechanics that have been in place from the beginning (limited rage loss from stance changes for warriors, no more ammo usage for hunters, etc).
I'll pop back onto this thread with 'holy crap!' at anything new that's huge.