I've recently bought the pangea software programming book. A very good purchase from what I've seen thus far, but the author's examples and tutorials are all done in basic C and use CGL to access OpenGL. Will this cause me problems later on when I begin to use the cocoa frameworks for OpenGL drawing? Is there a big difference?

Cocoa access OpenGL views in a slightly different way than Carbon, but OpenGL code is straight C and won't change between Cocoa/Carbon. Assuming you already know Objective-C and Cocoa, the switch shouldn't be difficult.

I converted our Carbon engine to Cocoa in a day. Most of the work was setting up a new project, which wasn't even required...