And, just to disagree with author, I'd recommend comparing Google's Picasa to itself.

That would be a fair comparison, because it is virtually the same application, with same set of features, done with online/offline UI's... slowly merging together.

BTW: as far as PC "desktop" software is concerned, Picasa is probably my favorite application. Even though I don't use it that much, but as an engineer concerned with usability, I always try to point our "desktop people"'s attention at it.