Ok, first off, you don't HAVE to upgrade to PCI-Express if you don't want to. That video card and mobo in your sig are VERY nice and would be just as good as any PCI-Express solution available.
Second, the main reason for the PCI-Express switch isn't just to replace AGP, its also replacing the extreemly old PCI I/O.
PCI-Express offers the availablity of much more bandwidth than either PCI or AGP so just because the performance isn't quite realized right NOW, doesn't mean that it will be really fast in the future. PCI-Express is still an infant compared to the "oldman" PCI and AGP, we need to wait for hardware and more importantly software manufacturers (i.e. games) to be able to produce things that can take advantage of the bandwidth. Its not gonna happen overnight, but it will.
The only reason to switch to PCI-Express right now is for futureproof ugradeability, not necessarily for any type of performance increase over AGP because video card manufacturers (and soon sound card and network card manufacturers) will be switching too and eventually will not even be offering AGP versions of their new generation cards so at that point you'd be forced to switch if you wanted to upgrade to one of those cards.
I agree that it may seem like the industry is kindof holding us in the palm of thier hand and telling us what to do, but I hope that a few years down the road PCI-Express will have matured more and its performance vs. AGP will seem uncomparable and we will WANT to switch.