I've tried planeshift ... there are 3 main problems with it as of now:
1) The Linux version is almost always released a long time after the Window$ version. Which sucks cuz you need the new client to play
2) Everyone in the game is not too nice. I've been there and I asked people simple questions ... their answers: RTFM ! And the manual is not very complete either, or at least it wasn't the last time I checked.
3) It's damn boring. Killing a rat with one eyeball for hours on end in order to get it's eyeball and possibly sell it to buy a cheap weapon so you can kill a bandit for a couple more hours ...
It'd be nice to see a good open-source 3D MMORPG ... but so far planeshift doesn't impress me much