I picked up Game Engine Architecture 2ed. the other day, written by Jason Gregory, the lead programmer over at Naughty Dog (they make the Uncharted series, and recently The Last Of Us).
In the first chapter, he breaks down some components of a typical 3D game engine, which includes character animation. He says of the Granny toolkit (developed by Casey); "In my opinion, the Granny SDK has the best-designed and most logical animation API of any I've seen, commercial or proprietary,..."
Just thought it was a neat find; I guess we should listen to Casey when he talks about compression-oriented programming and writing the usage code first ;)