Jim Louderback has delved into and written a lot about Microsoft Vista. He could be considered an expert. Here's his conclusion:

The upshot is that even after nine months, Vista just ain't cutting it. I definitely gave Microsoft too much of a free pass on this operating system: I expected it to get the kinks worked out more quickly. Boy, was I fooled! If Microsoft can't get Vista working, I might just do the unthinkable: I might move to Linux.

Or a Mac.