I've tried reading up on Core Animation, Quartz, OpenGL, and cocos2d. While I think I have a feeling what they're all meant for, I still can't decide what's appropriate for the project I'm undertaking. The requirements are straight forward, I need to be able to import a custom font and draw it. I need to draw lines and arcs.
I tried using OpenGL ES for this, but it was very hard to work in custom fonts. Between Quartz and Core Animation, I'm not sure what's applicable. The application will always be in 2D. Performance is important. I have a feeling Quartz might not be appropriate since you can use a finger swipe to move the screen to a different part of the content and it seems that redrawing that much content with Quartz is heavy on the GPU. Not sure though, this is all from reading.
The outlier is cocos, since it seems to fit into a couple different buckets. It seems closer to OpenGL, but without the insanity when it comes to loading in custom fonts. There didn't seem to be enough info to get a feel for whether it would fit for this project though.
I have pretty extensive experience with both Corona and Cocos2d. Corona is easy to use and great for a beginning programmer. There's a fairly large class of apps that you can write in Corona, but if you're looking for high performance, your best bet is Cocos2d. There's practically no 2D app you can think of that can't be written in Cocos2d. I recommend Steffan Itterheim's book if you're interested in learning it.
Best of luck!