So far, the beta seems to be coming along rather nicely. However, it's still got some problems and some that are not affecting the stable Windows release (that I am aware of). Some of the following issues may be posted elsewhere, but since we have no official bug tracker, I'll just list everything I've noticed, as I notice it.
* c2m5_concert rescue vehicle arrived on spawn of second finale tank. (single player/localhost) * Mouse input location for vocalize radials erratic. * Raw mouse input is extremely slow and erratic. * -high launch parameter causes extremely low framerate (15 fps, for me) * Occasionally, two mouse cursors appear on menus or Steam overlay, each tracking differently. (Noticed this on Killing Floor, as well. Looks like a Steam Beta bug, perhaps?) * Occasionally, combat shotgun audio becomes muffled. Switching weapons and back fixes.
The game is very playable on Linux on my low-end PC (even though there is never anyone online in the beta servers) and very enjoyable so far, outside of the above mentioned bugs and annoyances. I look forward to when it is stable enough for a proper release.
I will post my system specs and L4D2 config tonight, for more information.