I've been a software developer for 5 years now and wanting to get into iOS game development. I've played around with the iOS SDK for about 2 years now, attending cocoaheads meetings and feel I have a good grasp on objective-c/cocoa and even c/c++.

I have a game idea and know that I will use Box2D but I'm wondering if I should use cocos2D or not. The main reasons are:

1. I may want to do things graphics wise that aren't available in cocos2d.
2. If I roll my own game engine I'll have more control.

Of course the main reason for using a already existing game engine is the time it saves and it makes the hard stuff easier, but for someone who has the technical chops to roll his own does it make sense?