Oh well, canceled my iMac 3.06 intel core 2 duo, 1tb HD, 4GB ram, nVidia GeForce GT 130 512MB order today (Didn't have to pay restock or return shipping).
Got same setup w the ATI Radeon HD 4850 512MB instead...These things aren't cheap, so the $50 extra, and 3-5 week wait, for what I've read to be the best current graphics card Mac has by far (in post after post), I think I made the right move.
For whatever its worth...
Benchmarks of those GPUs are almost the same. GT130 (aka 9800M GTS) is desktop card so it's produces more heat (60W) and needs more power. 4850 is mobility card which is very energy efficient (about 45W).
4850 is little bit faster, so if you want to wait, that's the way to go.