You can argue the merit of allot of changes, but I think we can all be really glad they changed.
-(Hunter) Pets running away if you didn't feed them often enough.
-Ammo/Arrow Bags. Ammo/Arrows in general.
-Rogues needing to keep stacks of throwing daggers.
-Warlocks losing bag space to soulstones
(Yes I realize most of mine are bag space related. I had tiny bags in Vanilla.)
Your own recollections, please!