Keep XP, How 'bout 2000?
I likely will not be buying my first Windows 7 until, as I did with XP, about SP2. I have a graphics program that I have been using since DOS 5/Windows 3.11, and a flatbed scanner that performs circles around the current crop of "all-in-one" PSCs. Neither of these items will run even on XP, therefore I must maintain a Windows 2000 machine. I know that eventually, I will be telling a similar story involving Windows XP and Windows 7 or Windows 8. Until that time comes, XP will remain my primary OS and 2000 will remain my legacy OS and I will experiment with Linux and Windows betas on a spare computer. Up through today, I find nothing (not any linux, CERTAINLY not Vista, and still not Windows 7 RC) to replace this XP/2000 combination.
Windows 7 is no doubt a significant improvement over Vista, but a lot of Vista problems have just been "swept under the carpet" rather than being fixed.
That's my story, and I'm stickin' to it.