I agree with Radenight.
Microsoft have removed the shadow copy from 7, which, whilst it was a safety feature, caused a lot of negarive feedback.
Whilst the 7 defrag does not show the pretty, but useless, picture of the little blocks moving around, it operates at the same speed as the one that was originally in XP. Try it on a freash install if you doubt.
The 7, and Vista, defrag operates in a way which is particularly suitable for the OS. It also operates on a very low priority, so you can carry on with your normal work. Once you have completed the initial defrag, which can take a while, as it did in XP, if you then set it on a weekly schedule, you will not even notice its presence.
If you are interested in the full story, read this: Engineering Windows 7 : Disk Defragmentation ÃƒÂ¢Ã¢â€šÂ¬Ã¢â‚¬Å“ Background and Engineering the Windows 7 Improvements