Me, I'm joining the new user contingent in a sense and not upgrading either TTP or DW until I must, and that may be several paid upgrades from now. (The availability of both utilities via d/l rather than snail mail as was once the case makes that position even more tenable: as long as you've got a bootable volume you can get the latest version of either utility within minutes of your needing it.)
The problem is that you may not be able to access those apps if your data are so damaged that normal operations are impossible.
That said, I have noticed that Disk Warrior rarely finds anything amiss after Leopard. Snowy was very, very stable, and El Cap is at least its equal (as was Yosemite) in that regard. I run DW once in awhile for kicks. I never used Lion, Mountain Lion, or Mavericks so I can't comment about them.
