I can't reproduce this. I wonder if you have a rouge config.cfg causing this issue (from other bugs to do with where we save files, now all fixed). Can you look for a config.cfg under ~/Library/Application Support/Steam/SteamApps/common/Half-Life and delete/rename any not in the valve/ or cstrike/ folder please.
OK, I checked for rogue config.cfg files and sure enough I had three. I deleted them and now the sliders work, thanks!
okay, this bug is :
only load config.cfg from GAMECONFIG
Cool, to be clear I found the three rogue config.cfg files in these folders; cstrike_hd, valve_hd, and the root of the Half-life folder.
Nothing extracted yet.
The Gamma and Brightness controls in the options menu reset themselves to the max setting regardless of what I set them to in the Mac build. Note that the gamma and brightness level may change, it's just that the menu slider does not reflect it. This does not occur in the CS Mac Beta.