Stuart, I completely see your point (like I said, for how I ride, the tried and true cantis and Vs are fine for me) but isnt it fair to say that mtn bikers have been using discs now for years? And they toss themselves into the weeds all the time-so from my inexperienced view, doesnt it seem that mtn bikers have been putting discs to the best "worst case" scenarios already?

It may be that as I dont follow mtn biking enough, I dont hear of the "unrideable" cases enough, or of damaged parts that have to be replaced.
(again, at this point with my inexperience, keeping it simple and something I know is fine, but it really does seem to me that mtn biking must be the toughest test for these sort of issues that are coming up here.)