Its editing paradigm is strictly linear, but for $30 Quicktime Pro let me stitch together a series of short .MOV files, with audio, then add a background soundtrack under the whole thing. That was all I needed. Unlike the "real" video editors I tried, Quicktime Pro seemed to be merely combining digital files, resulting in no degradation of image quality at all.
EDIT: Here's a screen capture comparison of my attempt at getting a high quality .mov file using the trial version of Cyberlink Power Director 8, versus the smaller file size and sharper output of Quicktime Pro.

I did lose a little quality later, doing a smaller-file-size export for upload to YouTube, but it still looked a lot better than the output of other low-end video editing software I tried.