While Core Animation is an extremely impressive API and it will be the cause of a huge leap forward in UI design for OS X, it is not without its faults. As you have probably already discovered from the discussion of explicit animations, some of the ways that things need to be dealt with are quite awkward. Forcing us to add a delegate just to get an explicit animation to be made permanent seems overly clunky.
Likewise, there are a lot of calls to Core Foundation objects needed. Images and Colors, as well as other objects, are Core Foundation objects instead of Cocoa/NSObjects. While I am sure there is a good reason for this, interaction with OpenGL, memory usage, or some other purpose, it does make the API a bit jarring. Having to switch back and forth between Objective-C and raw C code does make it clunkier than it could be.
Having said that, this is version 1.0 of Core Animation and as history has shown us, it will improve in huge leaps with each iteration.