I admin for eGO (edgegamers.org) and play DOD:S all the time. It's "old school" FPS but its built on top of the Half-Life 2 engine.
It runs fine on a Mac with the proper settings using Steam OSX or via the Windows version under Bootcamp. I do get an occasional hiccup when playing the native Mac version but it goes away if you turn off AA and revert to medium rather than high settings for details, shaders, etc.
Great game, come join one of our servers sometime....all servers linked from our home page.