The Q3 Macintosh demo has been released, I included the original story here for you guys to mess with.   Firstly John Carmack talks quite a bit about the demo and performance on what machines you can expect. and then Graeme on the Mac version and drivers you will need.

The game remains very marginal in playability on 266mhz imacs and iBooks. A 333mhz imac should be playable for a casual gamer if the graphics options are turned down to the "fastest" setting. There is still a lot of room for improvement on ATI's side with the RagePro drivers. Almost all the effort so far has been on the Rage128 drivers. The G3 systems run fine, but a little slower than a pc of equal mhz
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From Graeme: You'll need the newest version of OpenGL for the Macintosh, which came out today. It's available at http://asu.info.apple.com/swupdates.nsf/artnum/n11545" rel="nofollow" target="_blank" class="external. Go download that while we're coordinating on getting the Mac build out there through Sandpiper.