The Inq learned about 70 percent of the upgrade market is still AGP, and not PCI Express.
There are far too many people using AGP systems that will try to get the new graphic card for the Yule shopping madness. Nvidia just cannot fill the demand and is still struggling to get its 6800 GS AGP cards out while ATI is happy with its X800 GT, GTO, XL sales. Those cards are all native AGP but some of them can be bridged with the Rialto.
When it comes to the entry level, ATI has Radeon 9550 while Nvidia wants to fight this market with 6600 chips but just cannot get enough of them. The demand is too great.