PCI Express vs AGP

I'm planning to buy a new graphics card in a month or so and I've been hearing about PCI Express. I hear its 16x but also requires a Motherboard with a PCI Express slot in order to be able to use it. I plan to spend a few hundred, maybe slightly more on a AGP card and don't really want to turn around and have to buy a new Motherboard just to use PCI Express right now.

I guess I want to learn a little more about it before I make a real decision so would it be worth waiting and buying PCI Express and a Motherboard to boot or will AGP be fine for now, maybe I can upgrade next year?

Pro and cons over AGP vs PCI Express anyone?

PCI Express will require you to buy a new motherboard.
There are certain models of motherboards that will allow you to use an agp or a pci-e or both (just not sli) at the same time.Look for an Uli chipset, maybe Asrock if you want to go that route.
Right now no games that I know of use the full 16 lanes in pci-e.

The advantages of PCIe over AGP are probably the same if not more than AGP over standard PCI. If your planning on upgrading (unless you get a great deal on an AGP card) I'd go ahead and save a little longer and upgrade the mobo and CPU too. Might also depend on your current system. If it's a few years old, it might be close to ugrade time anyway. If your using it for gaming, I'd say most definatly go PCIe. Newer games like BF2 won't look as good on an older AGP card. And the next generation of games will probably require PCIe to run on anything but low settings. And if you ever thought of running a dual card SLI set up, You'll have to have PCIe also. Even if you don't go with a SLI set up now, You can get one card now and add the second later. Spend a little extra now and will be cheaper to continue upgrading down the road. Atleast thats the way I'd look at it.
Here's a link that explains PCIe. http://www.pcstats.com/articleview.cfm?articleID=1087

Hope it helps.

PCIe with SLI support.