I am at level 44 right now on a PvE server that my (real-life) friends are one. I have not played in four years. I prefer RP-PvP servers, but I just walk around with my PvP flag on and I still get the occasional world action.
Here are my complaints:
* Multi-specing (pick a specialization and go with it, no two-build bull crap, everyone can be a holy priest and shadow priest with a click of a button. I want the old system back where you had to pay crap-loads of gold to switch)
*Map markers that point you where you need to go kill the incentive to explore
*Cross-realm battlegrounds and dungeons kill the sense of community and make it more difficult to meet new people. Most people I met were folks I quested with in dungeons, how I found my old guild, etc.
*Being able to join random dungeons from anywhere in the world kills any incentive not to just farm instances, thus fewer people questing in the world.
*You can have a toon on both factions on PvP servers now, no sense of real rivalry.
*Hyper-inflation has set in, Blizzard needs to make more money sinks to get gold out of circulation