I have. i can tell you it works fine but keep in mind its only multiplayer in beta and i was using steam to play it (not non steam version). as far as steam + multiplayer you should have no problems. as for singleplayer i have no clue
just wanted to say that I saw that the beta was available for free on steam. so I just downloaded it and it runs amazingly smooth - really well programmed it seems. I hope it still runs that smooth when the final graphics and dx10 are coming (=release), but it's really great.