I tried to update to beta 5 today and yesterday (2 clean installs, also tried to update from beta 4). The interface is extremely dark, next to unplayable. When I reversed back to beta 4 - everything is normal again.
I'll be more than glad to send you a dxdiag report/output log/any other piece of information that can help. Just tell me what to send and where. Granted, this is an old laptop and not gaming equipment, but I used to play the game just fine with integrated Intel HD 3000 card. I also tried running it with dedicated Nvidia card (dual graphic card laptop) - same result. Obviously, monitor brightness hasn't been tweaked and other than in-game there's no change whatsoever.
One more thing to notice: when I update from beta 4 to 5, there's an error at first try (corrupt content file), but then Steam re-downloads the patch and that's what I get. Clean install, as I mentioned, gave the same result. Validation of game cache passes with no errors.
Two screenshots for comparison:
Thanks in advance for any help!