AGP as a standard has been replaced by PCI in the mainstream, but those who have stalled on upgrading for one reason or another might now have an incentive to finally grab a PCI Express motherboard. BFG is offering people who have purchased an AGP-based BFG card in the past a free upgrade, replacing it with the PCI Express equivalent.
In some cases, the upgrade is not just an equivalent but rather a significant step up. The company is offering, for instance, to take a customer's GeForce 7600 GS OC 512MB AGP card for a GeForce 9500 GT OC 1GB PCIe card. Even at what is considered the "low end" of the spectrum the card maker has options available, with BFG offering a 9600 GT with 512MB of RAM in place of a 6800 OC 128MB. It certainly wouldn't be a completely "free" upgrade - you would still have to finally decide to purchase a PCIe board and handle all the other upgrades that go along with it. Still, it's a nice incentive.
BFG does require hardware registration to take advantage of the offer, though they do not require an original proof of purchase. You can learn more about this offer here.