I think it really depends. I really am happy with Windows 7 and I just built a machine in July and Windows 7 64-bit is exactly what I planned to put on it.
My wife has an HP laptop with Vista Home Premium 32-bit on it, and it's running perfectly fine. No problems, good performance and we have the super easy system restore utility from HP to snap back in the event that a major problem comes up. I simply see no reason to spend any money to move this from Vista to 7 on this machine. Therefore, this one is staying as Vista.