It really depends on the feature. A featurette pulled from the EPK? Once, and that's it. A 1hr+ detailed documentary? Maybe a few times. Storyboards? Probably one pass thru. An interesting commentary that's as enjoyable as the movie? At least more than twice and I rather have a good commentary...
Yeah, every dvd of a Pixar movie is a slam dunk when it first comes out, even the overcompressed Finding Nemo. I bet it's even "approaching HD" and "like looking into a window" too. :D