I've used Popcorn to make backups of a couple of commercial disks that were skipping in my cheapie DVD player. The first backup was fine, and did not skip at all, unlike the source. No problem with screen ratio, because the source was made for TV.

I noticed a problem on the other two disks, though: the correct aspect ratio of the source (widescreen) was lost once Popcorn had processed it. So Popcorn seems to be completely useless for backing up most movies, unless you just don't care about the quality.

I've posted a question about the widescreen problem elsewhere. One person responded that it's a Quicktime problem: that Popcorn uses QT for compression and that QT screws up the aspect ratio.

Sounds like DVD2One would be a better solution. Popcorn has major limitations.