I don't see many problems either, probably because I am a full-time GNU/Linux user, but another application that is often pointed out as difficult to use is The GIMP. I actually disagree with the premise that GIMP is hard to use, and find it quite intuitive for basic operations; most critiques actually complain that it doesn't have the Photoshop look&feel.

It often boils down to the difficult task of discerning usability, intuitiveness, efficiency, and familiarity.