The advantage to buzzsaw is that it defrags as files are edited -- realtime defrag.
That's precisely what I dislike in this program... let me explain :
I read your post and I thought "cool, a realtime defrag tool ... my HDD will never get fragmented again!"
Then I tried and install Buzzsaw along with Dirms, and found out that it was a good set of tools (and free, moreover)
However, there is a price to pay : with a real-time defragmenter, the defragmentation time is paid by the user, in the form of slower access to its files, slower copy, etc... With a "classic" defrag tool (e.g. DiskKeeper, Norton, MS defrag), the defrag time can be setup to happen after hours (at night, or during lunch).
I configure DK to run in "screensaver mode", and it's been quite efficient (although I think a better defrag tool could do a better job, my laptop seems a bit slow).
Anyway, this was just my two cents : Dirms and Buzzsaw are great program nonetheless ;o)