I've been running vista ultimate edition since it came out and I'll say this for Vista, the search engine kicks ass. If you take the time to add meta tags to your files, the search functionality is very powerful and useful and the fact that the meta tags are written to the file itself, means you can transfer files around and still retain them.
Other than that though, I really haven't seen much benefit to Vista over XP. It's slower, it needs more system resources, it's still buggy, and if you're running older hardware, especially laptops, driver support just sucks.