I never used to do it but have recently been doing it on a regular basis. Some people say you don't need it and others say you do. My computer start and shutdown quicker than before. I'm glad to hear from another user that does it regularly.
It was a hassle using the built-in defrag because you have to remember to do it and it slowed down the computer when it's running. I got a third party defrag program and scheduled the defrag so I don't have to worry about running it.