It IS out for Macs, and it's great 🙂 I never tried a class-based shooter before but I'm hooked.
The patch is for the FULL game, not for the demo. (Which, as stated above, doesn't exist--at least not yet.)
If you want to try it before buying you'll have to wait for a demo. But you can BUY it now. Amazon has it, for instance.
As a general performance test, the Quake 4 demo (see macgamefiles.com) performs generally similar in terms of framerates. It uses a similar engine. But the gameplay of Quake 4 is a linear one-player "quest" nothing to do with the team-oriented Quake Wars.