I'm on mysidea, the 2nd most populated server. Selbina is the highest, and I think besaid the 3rd highest, last i checked at least.
Bare in mind, the game is not *perfect*, but with proper expectations, it's a **** of a lot of fun. Everything functions without bugs or glitches, and the world is beautiful. On conjuror I can cure-bot in a party, on marauder I can kick everything in sight's ***. There's a lot of content, I have done a ton of quests, saw beautiful cutscenes, etc. I have a couple blog posts at http://www.pocket-hockey.com
that describe my experiences, with lots of screen shots, if you're interested in some more in depth details.