Loved this game for a long time but since you asked...........
Letting people have horde and alliance chars on a pvp server.
Flying mounts.
The leveling process has become so trivial. Just get to max lvl and collect marks or whatever.
For me, the game was always 1-60. I'd stop at 18,28,38 and so on to pvp for a few weeks. Took me months and months to get to 60. now?
not worth it at all....