Type Vista in the search box on the left of this page. You will find that as fo3nix says, many have, and all regret it.
If you wonder why such a lousy product is being pushed by so many people in the industry, just think on the fact that according to MS' own figures, for every dollar they make from selling it, the rest of the industry will make 700 from supporting it, providing upgraded hardware to run it, and so on...
Thanks for the link. Had a comp with windows vista until this morning. Only had it 3 days and couldn't understand why it was running so slow. After reading all other comments in the links, my comp was returned today and I have now got a new one with good old windows XP.