This means that even though the early apps will have a definite advantage, there will always be an opportunity to make a 'better' tip calculator (contrived example) and new opportunities will open up as the platform matures.
IMHO, iPhone apps are a much bigger deal than facebook apps since all the latter seem to do these days is clutter your profile and make you waste time.
So, honestly, go out there, 1. find a problem (like mass transit directions) 2. solve it with an iPhone app. 3. PROFIT !!!