lxm7 : worked with iOS, iPhones and iPads for a client, with C2.
For optimal performances : don't use physics and no viewport/texture, anything graphical over 1024x1024 (the viewport is flattened as an OpenGL texture by the system, so you don't wan to force the GPU to create another texture).
If you create an app with PhoneGap, or asking the user to create a bookmark on the Homescreen, remember that the Nitro Javascript engine isn't activated for those use cases, so it's going to be slower.
On mobile : only one sound at a time and preload lag for that sound, so you perhaps need to use an audiosprite.
That's what I'm thinking for the moment...