I've been in the last few PC beta weekends, and have been in the alpha for a couple weeks (not really alpha, just a live test environment that the devs update more often, and is up 24/7). It's tough putting too much time into it though because I've already done the early game stuff several times. The game is pretty decent, though not amazing. I can see it being a lot of fun with a friend or two. There's the main story missions, which are mostly phased (your own version of the overworld area where it takes place), and tons of side missions. World events (arkfalls) like in Rift or the old undead invasion that happens way back in WoW. You can queue up for pvp matches, or join in an open world pvp mode with capture points. (takes place in the questing areas, not a dedicated pvp location, but you have to queue for it and it only starts when there's enough people.)
I've been trying to get on the Xbox 360 beta since it started yesterday, with zero luck so far. There's some issue where it tells you, "A sign-in change has occurred. Returning to title screen." and you never get in. My friend that was thinking of buying it doesn't have a PC and we play everything on Xbox, so we were thinking of getting it there.