Well, I purchased a ATI Radeon X1650 Pro 512MB Video Card at Circuit City this weekend, and despite massive installation issues, managed to get hardware rotation to work quite well. It's really over-kill for MAME, but hey, it works.
Visual pinball, MAME, and Fusion are all working very well rotated 90 degrees via irotate.
I prefer Nvidia over ATI Radeon because of their "better" linux support, but until Nvidia fixes their hardware acceleration while rotated, I'll be sticking with my ATI card....
Hope this helps someone out there...