At this point, I don't think "leveling" should be considered a game mechanic -- there are so many apps and things that I can "level" in that leveling has become... ubiquitous, I guess, and therefor uninteresting. Achievements are kind of getting the same way.

Game mechanics only work if they're interesting and motivating. When something becomes uninteresting, I don't think it should be considered a "game mechanic."