FraterPerdurabo: I'm on EU Outland PVP (Alliance).
I'm not a regular player, just reactivated for a month after about a 6 month hiatus... I typically catch up with all of the content within that month and then get bored again. Get some achievements done and that's all.
And I don't think I'll be playing much now because of D3.
As for the server, it used to have a great scene for high-end raiding, I think it was ranked ~top5 in Europe in terms of raiding progress. It's a very packed server and the battlegroup (Misery) is the single most popular battlegroup in terms of arena games played (at least used to be). Also in the BG are many other high-end raiding servers (i.e. Veknilash) so there are fewer scrubs around, but obviously the bar is higher. Easy to get groups for pretty much anything (though not sure how that works for a mage). Lots of raids around, lots of pugs.
Back in WOTLK it used to have a lot of issues with lag, fortunately I don't think this is the issue any more.
There are also occasional queues during peak times, but to be honest, I haven't had to wait for more than 15min.
I've checked the server populations and it seems that Alliance quite outnumber Horde on Outland
Not that I'm complaining, since I love doing PVP that will mean more alliance for me to kill
I'm quite interested in how Blizz will also implement cross realm zones in MoP, who knows, maybe it's gonna be just like the old days of Hillsbrad and Southshore in 2005