This forum post (linked from Xlr8yourmac.com) by Epic VP Mark Rein indicates that the Mac Demo of UT2003 may be released this week:
Ryan Gordon let me know this morning that he has sent a version of the Macintosh UT2003 demo to Macsoft that is ready for large scale testing in the hands of Mac users everywhere. Macsoft will be doing some testing on this and creating an installer for it but hopefully this week the Mac demo of UT2003 will be released. Once the demo is out Macsoft will be collecting bug reports and feeding them back to us so we can promptly fix them and finish the game for retail release.
You will definitely want to update to OS 10.2.5 to take advantage of the latest Mac OpenGL code - especially if you're using an ATI graphics card as prior versions of OS 10.2 had performance issues with ATI cards when running UT2003.
