I have a decent amount of faith in the recommended temp range, compatibilities, etc... but the stocking % scares me. I think it still uses a lot of the "inch per gallon" metrics which is an old school idea that doesn't always apply. An example I heard someone make yesterday was that ten 1" fish in a 10 gallon is fine, but a 10" Oscar in a 10 gallon is insanity.
IMO, I believe stocking comes down to filtration, dedication to maintenance and weekly pwc's, swim room and common sense. I trust my own eyes and the people on AA who have personal experience more than I'll ever trust an automated compatibility and stocking calculator which doesn't take near all the variables into account.
Like I said, it's fun to play with though