I have been doing the beta for a couple of weeks and found it to be working smoothly...which amazed me for 2 reasons. One, I am a Linux newb who had to do a bunch of research, dig up a older rig out of the garage, install the OS for the first time in my life, and then install Steam without having actually used the OS for anything of real importance. The second reason was because the various forum threads have long posts from individuals who very much sound like they know what they are talking about and are reporting having multiple problems.
Lucky I guess. Was also cool to play Serious Sam 3 for the first time.