The superman punch has it's applications, it's just not the most effecient strike out there. You may be able to catch someone sleeping, or if you've set them up to expect something else (as mrmyz accounts his use of it).
On that end, I would like to ask mrmyz if he's referring to the "skip punch" being thrown with the lead or rear hand. When I see most "superman punches" thrown in MMA, it's usually a lunging cross with the rear hand. When I read "skip punch" I envision what Bruce Lee called his "straight blast," the JKD Lead Straight.
Myself, I'm more of a fan of the Straight Blast.
It doesn't matter if you agree or disagree
... As long as I don't bore you and I spark a moment of thought, my goal is achieved
Queng leon queng tigre ecu tacacut, queca pa? - Pampangan Mandarigma Motto