In a word: Deep!
Although easy to get started with, Anime Studio Pro is very deep. It has a lot of the very high end features that I have used in After Effects and Lightwave. Things like particle animation, morphing, lip synch, tracking, bones, and 3D planes. Actually about half of these things are in Lightwave and the other half in AE, but ASP has them all and they are much easier to use. ASP will work with vector layers as well as image layers, it will bring in movies which you can work with, and particle layers can make water, sparks, smoke, or even crowds. It will even bring in 3D objects and can work with them in a limited manner. ASP has audio layers and some nice lip synch tools and plugins.
