Checkout CocoonJS demos and their own published games in the AppStore , you will see it's capabilities. The newer version of CocoonJS which will be releasing soon has lot more capabilities added and performance improvements to be able to compete with main stream games.
Ashley , one suggestion , you should make a Angry Birds like prototype in C2 to show case which will make people totally believe in the tool <img src="smileys/smiley1.gif" border="0" align="middle" />