My rig is five years plus. It came with Windows XP. It was very EASY to resist upgrading to Vista. I believe my resistance to Vista saved me a lot of frustration.
But I am more than willing to go to Windows 7 at some point, feeling that I dodged a bullet by skipping Vista.
But one, my rig is running flawlessly. I have upgraded the power supply, maxed out the memory and have about as up to date video cards as the machine can handle.
If I have learned anything about Microsoft, it is NEVER TRUST them to deliver any worthwhile product on its introduction.
I would say that some time in 2010 if they get whatever bugs there will surely be worked out, I am ready to get a new computer with Windows 7.
Six years for a computer is pretty good in IMHO. But I agree with what Mossberg said that buying a new computer with Windows 7 should be considered.
In the Windows world, one need not get to attached to the hardware which is really quite cheap in price, it is all about the operating system.
I doubt if I would ever buy a new engine for a six year old car, neither would I try to go to Windows 7 from XP.