Features:

easy to learn and use, hard to misuse
pure and clean Objective C
blending seamlessly with Cocoa
no need to write any OpenGL code, but:
easy to extend, even with custom OpenGL code
allowing direct use of iPhone features like accelerometer or vibration – no need for a wrapper!
leveraging your existing Flash/Flex skills (no need to learn a new API!)
Open Source, compatible even with closed source commercial projects

supports iPhone / iPod Touch / iPad
hierarchical display tree
fast and flexible animation system with custom transitions
each numeric property of any object can be animated
powerful event system supporting custom events and “bubbling” along a responder chain
(multi)touch events are directly bound to the display tree
fast texturing, transparently supporting subtextures
texture atlas support
manipulation and animation of texture coordinates
text rendering, supporting TrueType and bitmap fonts
easy to use, fast audio support

Features