What I like best is the simplicity of the user interface which allows for the creation of complex animations.

Hype gets the job done right. This program is efficient, easy to use, and simply makes sense.

I started use Tumult Hype a few months ago, it's absolutely useful. This keyframe-based animation gives the opportunity to create simple animation (and use them into a GIF) or project more complex project for Web. The whole interface is simple and after several days of study to become familiar with It the fun begins. I recommend the PRO version because it has more features (Psysical Engine, for example) than the basic version. It's perfect for my business use.