The short and long of AGP and PCIE.
Short:
Marketing is clearly saying we want to change to PCIE because it's the new tech on the block. PCIE also allows for SLI/Crossfire, which is fast and cutting edge. Marketing likes to sell cutting edge, because they get to work on new powerpoint slides that dump on "The others guys".
Long:
AGP versus PCIE is a moot arguement. PCIE is more than just a video slot, and allows for substaintial growth in bus bandwidth usage. It's a future technology that will eventually replace AGP and conventional PCI busses. Simplifying and converging these busses (at the present time) seems like a good idea. Obviously at the current time the *only* function PCIE offers over PCI, AGP, PCI-X("Legacy Busses") is SLI/Crossfire. If you do not use more than a single video card configuration, and run applications at high resolutions PCIE is an unnecessary cost to a system. To me the zero benefit to switch to a PCIE board and purchase a PCIE card, other than the technological improvements in the new video card the PCIE bus gives me no performance increase whatsoever. Though like I said, marketing on both of the major sides is clearly showing they want to pump PCIE as the next coming. Sure people can offer up numbers for the sale of the top cards capable of PCIE SLI, that current AGP cards couldn't touch. Then those same people would have to realize the majority of these "big companies" profits come from low-mid range solutions. Just like Intel and AMD have their respective EE and FX editions. Nvidia and ATI's top cards offer nothing more then chest beating rights for themselves. Naturally there will always be people that want that "cutting edge" or receive it for free and are more than happy to use it. Their purchases are not changing the real focus of these companies, which is located in delivering the low-mid range products that Joe Sixpack will snap up in droves.