Justin Putney at Ajar Productions has created some amazing extensions that you can use with Flash CS4 and the new motion model to help with your tweens or create them. Justin’s extensions are not only useful, but well implemented and documented on his blog.
For some helpful detailed info about the extension creation, check out this post on the Ajar Productions site.
For information/download for the MotionSketch extension, which records/creates a tween based on you drawing in Flash (!), see this post.
For the Motion Blur extension, which analyzes the movement of your tween and then creates a motion blur. see this post.
Many thanks to Justin for your hard work, and excellent extensions.