With Monkey, when you build, it actually creates the native code for you right on your own computer, so if you want to add Game Center, or something to that affect, you could actually open the code in XCode and do what you need to do, no limitations - which is why I've become a fan actually.

I can open the code in Eclipse and add AdMob ads if I want to after I've created the game in Monkey.

The cool thing about Corona is how popular it's becoming, and how they are developing new features at lightning speed. As a subscriber, the daily builds are really impressive.