...DW used to be almost mandatory in a Mac tech's toolbox IMHO and my copy certainly did its fair share of repair and recovery over the years, but I haven't needed to do any update, but neither will I likely be exposed to any need to...
We had an interesting discussion on TidBITs Talk a while back, with the subject "Looking For Disk Warrior Justification." Maybe it is available in the list's archive.
The upshot of it was that back in the days of the Classic Mac OS, Apple's included Disk First Aid wasn't particularly effective, and that disk problems came up often enough that Disk Warrior (or similar, but DW was the most popular), was both a godsend and almost a necessity.
Parenthetically, I remember that on most large Macintosh discussion lists, back years ago, about once or twice a month there used to be a message from some user whose hard drive had apparently "died" and that DW almost miraculously resurrected it. That was impressive, but I haven't seen a post like that on a Mac discussion list in years now.
Nowadays the Mac OS is quite a bit more stable and reliable, Disk Utility/First Aid usually works well when needed, and a utility such as Disk Warrior is rarely necessary for your average user. On top of that, Disk Warrior is now $125. For $125 these days, instead of purchasing Disk Warrior, assuming that you have a back up of your data (and you should) you can instead just purchase a nice replacement hard drive, which in my mind is a much better value, because once a disk fails so badly that Disk Warrior is necessary to repair it, can you ever really trust it again?