Anime Studio Pro is a product with a long history and a reputation to accompany it. It is a 2D vector based animation program created over a decade ago which since then has gone through a lot of changes and upgrades. Current version includes all the right features, such as physics emulation, 3D model support and creation, a Character Wizard for design editing and many more.
One of the most welcomed aspects of this program is that it is compatible with Photoshop, having a layered import process. There's also a Smart Bone system which shortens the animation creation process, reducing both time and frustration. Editable Motion Graphs make the resulting animation smoother and more precise. I should also mention that the earlier versions of Anime Studio Pro were the first to include support for Poser and Wacom tablets.
The most appealing aspect of this suite is that it can actually let people make animation that looks professional. Not every tool lets you actually be good at what you do, but Anime Studio Pro has all the right things. The interface, which is being updated and perfected with each new version, makes it easy to do a good job and access even the most advanced and special processes that make great animation.
Anime Studio Pro is not cheap and, despite the great job the developers do on the interface, can be quite difficult to master properly, but if you want to create animation, this is the right tool.