v2.0 is no compatible with OpenGL ES 1.1. It only use OpenGL ES 2.0
I think there are still millions of devices in opengl1.1 (iPhone 3G), we don’t want to miss them.
Yes, it’s VERY VERY essential for the iOS development at the moment. Actually, it was great surprise for me, when I’ve switched to the new cocos2d-x 2.0 and in the end of this process found, that old generation devices, which has iOS 4 installed, can’t run cocos2d-x 2.0, because OpenGL ES 2.0 is missed.
I think, that you need to note somewhere on the main page, that backward compatibly is broken in v 2.0 for devices without OpenGL ES 2.0