I've continued with the Tabula Rasa beta, and my verdict is that one is a keeper when it goes live. It reminds me of AO in some ways and I suspect there's elements of Planetside in there, but I've never played that one.
Even for a beta, it seems to run rather well and my rig can push the detail settings right up. For me, it's a nice sci-fi setting which is what I prefer over the fantasy theme, seems to have enough to do, though the UI takes some getting used to. If they squash a few bugs, a tweak here and there, they've got a very solid base to expand on and plug more content in as the game progresses.