I wonder how this compares to monetizing iOS apps with in-app purchases of game currency and/or items (or even Rovio's "Mighty Eagle"). There seems to be some market in games that would be called casual games (in my understanding, all iOS games are pretty much for the casual gamer) for those who get frustrated to pay real money for some advancement.

I personally don't like it, though, and would never pay extra money to skip playing the game since that seems counter productive to the purpose of a game. If the game isn't interesting enough to play, then I just play a different game. It's not like I don't have enough choices.