Dually with 2 - 850Mhz PIIIs. After I'm done the wife and kids use it, so 5 years is a minimum.
Haven't had time to play many games recently, but may have to make an exception for HL2.
Used mostly for document image management, web site development, increasing involvement with digital images and video, some games, general business apps. The current system is pretty much out of gas, especially when my work with digital images and video ramps up.
I may not want to wait for a second wave, which is the smart move, but build twice. Now and in a while.
I was waiting until the 64bit technology had time to effect the market and the 3Ghz or above was the sweet spot from a price/performance perspective, but then these BTX and PCI Express issues poped up. I'll decide when to jump on this speeding train soon.
cheers!