What programs are Mac OS X users using for managing their photos?

A friend was using iPhoto, and he cropped an image (intending to zoom)
and when he moved on to the next image in the directory iPhoto
automatically overwrote the original! Fortunately this wasn't an
important image (a test shot in a series to determine how noisy his
camera is when shooting long exposures in low light, a test he's going
to repeat anyway), but IMHO this is NOT desired behavior for serious
image management software.

He also has C1-Pro and has given it a brief look. The "session"
concept is a bit confusing and I'm not sure that this is ideal for his
needs.

What other software programs do Mac users suggest he should consider?

jc