I had Win95 for years and saw no reason to upgrade. Then I saw WinXP on a friend's PC. Initially, I thought that it was too 'cartoony' but was won over by its stability and, eventually, even its visual layout as it is not that different from W95 and can be made to look like it [mine does!].
In the end, I had one Blue Screen Of Death too many and took the plunge - and now I am very glad I did.
If Vista is only superfically different, then I won't be changing. I have no use for Media Centre gimmicks nor for an in-built DVD burner - so what IS so different to make me want to pay out and change?