I have now installed this on my Hackintosh with a ATI 4850 card. I have two partitions with SL installed on them, one for testing and one for production. Once I tested this out, I ended up using MultiBeast's "ATI 48xx Device Injector" on my production partition. I previously hand edited the IOPCIMatch string directly in the ATI4800Controller.kext, but this did not work in my setup.
My successful install went as follows:
1) Run MultiBeast 2.1.4. Ok through initial prompts to selection area.
2) Run manually downloaded Graphics Update package, and have it install.
3) Once it is at the 'Restart' prompt, switch to MultiBeast, select the "ATI 48xx Device Injector" and "System Utilities", and run it until it quits.
4) Restart from the Graphics Update installer.
Everything is working correctly. Chess has nice reflections, there is a translucent menu bar, and I get the waves when I drop a new widget. Because I install them twice, I always manually download and run updates from Apple.