Without wanting to sound contrary, I think it depends on your current setup. At one point I had an "okay" CPU and a good video card. It helped me much more to get a newer CPU for use in AH than a newer video card.
AGP is only a waste if you're building a new system from scratch. If your existing system needs an upgrade, then AGP has cards that will last you for a couple more years (if you can't afford to switch). My sister has a 5-year-old system that we needed to revitalize. We put in a new(er) AGP card, and viola. We can't afford to get a new system because then you'd have to do it from the ground up (or is that "from the case up?")
You're right that it is a dead end, though. Limited returns compared to the selection available in PCIe.
