1. Dont know I've only ever toyed with zercher's ever tried to load up like crazy, I've been able to use 225 for reps without too much of an issue but never tried going above it.
2. Well if you were to believe Pavel it's good for everything http://www.strongfirst.com/blog/the-best-squat/
But in all honestly I have used it during my deload weeks, or for fun as a conditioning thing. I wouldn't replace BS or FS with the Zercher if you are into Oly or PL'ing. I've heard good things about zercher for Strongman though.
Check out this old thread about Zerchers with some good posts by DVS: