Some perspective on those bad reviews: V1 once posted that DW was about to erase the HDD he was working on when he noticed it in the old/new comparison.
Never skip the step!
But to give you some perspective on whether or not to spend $120 on DW I'll ask if anybody has actually NEEDED it recently, or is everybody just stuck in the periodic maintenance routine and using it solely for that purpose? I don't recall a single problem that's required DW's intervention having been posted in a looong time.
Back in the days when OS X was far less stable than it is today, when I didn't have an external bootable volume, and when DW could be acquired only by snail mail, I considered it to be an extremely worthwhile investment.
Today, those factors have been all but completely resolved, and DW can be acquired immediately upon need and is, therefore, unnecessary up-front insurance. (Just my take on it; I've never upgraded from DW v 4 or TechTool Pro v 6.)
