1.) My favorite changes were the newly added battlegrounds, and raid content, least favorite, the majority of stat/class changes, at least to the classes I play. 2.) I'm looking forward to playing a druid again, as well as the monk, which was fun for all 2 lagging hours I was able to get in during the beta :)
I came into this expansion when t13 became easy after a year or so hiatus. It'll be nice to be pushing through new content. I'm glad to hear that you're happy with druids coming up. I was kinda disappointed with them in this expansion.
I know this is an incredibly broad question, but how is WoW these days? I haven't played since I finished WotLK raid content before the cata release and I'm debating coming back to it. I used to play a cat/bear druid, a disc priest, a holy/prot pally and an affliction warlock.
To be honest, as someone whose played since release, cata is horrid. End game content is basically a Heroic dungeon, it's easy. Not much to do now until mist. I'd wait until MOP if I were you, unless you want to gear & get 85. Most classes were changed & nothing like they were in LK, especially Druids & locks. Priest dps is OP as heck though.
The only reason I even think of playing WoW anymore is because my friends that play it and I know a lot of them who tend to only play for a few months an expansion, then wait, maybe come back to check out patches. If they could come back for a week instead of a month I bet they would. (Payment wise.)
I completely agree with Klaatu24. I've also been playing since vanilla and this is my least favorite expansion. They have done a few things right though which I hope they will perfect in MoP. I recommend starting at the beginning of September to level up your characters and get a feel for this expansion before they change everything.
One of my favorite changes wold prolly be the Pet Battles (Pokemon), and least would have to be fixing of stats like every expansion =/. And I'm definitely looking forward to hopefully owning it up on my boomkin again.