Correct me if I am wrong, but I think I read about a project between NVidia and another company (lol) to release a new 3d-api for Apple, since windows directx is too strong in the pc-market. Currently there is just OpenGl for Apple (as far as I know) and it's not supporting all the features of the new highend graphic-cards.
This new api should be optimized just for Geforce cards, of course. If that's more than a rumor, I would consider Geforce cards too, eventhough the ati 9700pro is very powerful. And the new pbooks going for NVidia than ati looks pretty interesting...
iBook 600; 12''; 640mb; 8mb Rage; DVD-CDRW-Combo, 20GB
P4 1.6; 2x80GB Raid1 (file-server)
tiBook 1Ghz, Superdrive, 768MB, 64mb 9000, 60GB