I wouldn't go so far as to say that the Norton defrag utility is good. I'm amazed how much stuff you have to go through just to get a defrag. You have to run several utilities that resulted in some mixed-mixed up data in Quicken. In the end, it optimization wasn't that good either.
I've heard alot of good comments for DiskWarrior by Alsoft (www.alsoft.com). It also got a great review in this months MacAddict. If you're looking for a less expensive solution (DiskWarrior is $70), Alsoft also makes just a defragger called PlusOptimizer (only $30). I haven't heard any comments or reviews but Alsoft seems to be a good company.