I'm particularly interested in group/raid combat and guild support structures i.e. how easy it is to manage and interact with other people in a guild/raid way in-game.
It's tricky to compare with WoW, I'd say - not only because of my very limited experience with WoW, but also because there are no mods yet. The basic interface isn't superb, but it isn't bad either. I haven't looked through it properly yet, either. And I haven't been in any larger groups - still on "newb island".
So far, what I can definitely say is that for anyone not already having a particular interest in this game, it's probably best to wait a few updates. There are quite a few fixes outstanding, even though I'd still say it's better off than WoW was when it launched.
For In-depth commentary on guild/raid topics, you'll have to wait until I've leveled up a bit What I can say right now, however, is that the classes seem to work well with one another. And that it's fun ^^. I haven't experienced any lag, and re "everything is an instance" - well, that's _postitive_ imho - it's never too crowded. And that nearly all feats are the same, well I've only seen the priests' feats, and they vary quite a lot. And I'm fairly sure the ranger doesn't have my spells. There is a "general" feat category, and they definitely are alike between the classes, but that's sort of the point I guess.
I'll post up more when I've played some more