It's coming about time to upgrade my computer. Morbo has served me well for many, many years now, but the last real upgrade it got was a new video card two and a half years ago. I'm actually considering the idea of buying a pre-built machine this time. A year ago this would have sounded insane—why buy when you can build?—but maybe it isn't. I've heard recently that it can actually be cheaper to buy from Dell than to build yourself, due to their wacky bulk hardware deals. I'm skeptical, as that has never, ever been the general case, excepting perhaps insane doorbuster Christmas sales. But, it's worth looking into, I suppose.
I think I want to wait until DX10 video cards come out. I don't really know anything about PCIe... I assume that I can't use an AGP card in the meantime while I wait for DX10 cards to exist. If I could, I'd buy sooner rather than later. Let me know if you know either way, so I don't have to do the research myself. :)