El Reg has an article on Windows Vista's file deletion problems, mostly related to the inordinate amount of time taken for what should be simple file operations, moving / deleting / copying files around. I see this all the time and it's a immensely painful experience when it takes 15 seconds to delete a 100kb file on a dual core 2.40Ghz machine with 2G of RAM.
To prove the point, one user found the problem went away when he ran an XP Pro Virtual Machine that was running on top of Vista. Mysteriously, it took him about eight seconds to delete the 23GB of files he wanted to get rid of. Using Vista on the same machine took him more than 25 minutes.
Interesting reading if you're using Vista and wondering if you're the only one having these issues, or if you're thinking of switching.