Apple - iPhoto - Feedback
One of the most time consuming aspects of digital photography is cropping images so they'll print at 4x6 sizes.
iPhoto has many performance problems, but one of the most serious is that on a 600MHz G3 it's quite slow to select a photo area, move the select box around, and crop. I spend seconds waiting for the iBook to respond to a cursor movement.
I think some usability studies and code optimization would really pay dividends in shortening this work. For example: a "quick crop" button that set a crop box to 4x6 or 6x4 in the center of the image.