It would be very easy to make a game like Chopper Rescue much simpler than it is. After all, a game where the main objective is to tap the screen in order to drop people from a helicopter to a waiting aircraft carrier below doesn't, on its surface, have a lot of challenge. At most, you might struggle with maneuvering the chopper directly over the target.
But Chopper Rescue is, in fact, quite challenging. This is, in large part, because it uses exaggerated water physics to tremendous effect. After the initial "getting to know you" levels, Chopper Rescue gets much trickier by having the ships you're landing on sway like madmen. Try maneuvering a moving chopper over a moving boat and landing your players onto targets not much larger than you are, and you've got yourself a game.
As the levels continue, additional elements that make the game a bit trickier enter into the mix, but, generally, what you see is what you get when it comes to Chopper Rescue. That's fine by me. I'll take a well-executed concept repeated with various challenges over numerous stale gameplay elements thrown around without care any day.
About the only thing that's a little frustrating with Chopper Rescue is its scoring system. Each level is scored based on an overall score plus a time bonus and a precision bonus. This intricate system is interesting, and ties in well with GameCenter, but it doesn't provide quite the same incentive that getting, say, three out of three stars does, in more-traditional app game scoring. Without looking at the leader boards on GameCenter there's no way to know exactly how well you did.
When my biggest complaint with a game is how well it scores a player's performance, I certainly think I've gotten my money's worth, and that's exactly how I felt playing Chopper Rescue. It doesn't use a number of different gameplay styles to keep you on your toes; rather it uses a simple, but effective, gameplay mechanic, and layers difficult challenges on top of that mechanic for a very enjoyable experience.