You can test how compatible your hardware and software is with Vista by running Microsoft's Vista Upgrade Advisor utility on your PC. You can get it here:
http://www.microsoft.com/windows/pro...deadvisor.mspx
I used it to test the five PCs in my office. Only one was hardware compliant and none were fully software compliant.
Sure I could upgrade the hardware on the four non-compliant PCs. However, all are over two years old and in need of replacement not upgrading so why waste the money?
And yes I could remove the non compliant software and substitute other programs. But the software I use is carefully chosen so why would I deliberately choose to replace it with something inferior? The more so when you consider that the software vendors will almost certainly release Vista compatible versions in the coming months.
This reasoning that applies to my computers will also apply to most users.
For most users, Windows Vista should not be seen as an upgrade option but rather a new computer option. The next computer you buy will come with Vista, it will have hardware designed for Vista and software that works with it. By then most of your current application software will have been updated to work with Vista as well.