You might want to test C4P, it has a ton of fixes really, and a lot of work has been done on the animation side of things. It also has several new features, like better terrain. Even if you are limited to rendering only 4 seconds of animation, and there is no saving of projects you can work with animation that is longer than 4 seconds in the demo. Importing your scene from one of the earlier versions is of course as simple as it always has been, just open. Only once have I encountered weird animation in cs3, and it was probably due to a hidden keyframe (a keyframe lower in the hierarchy that I couldn't see without opening the entire hierarchy), which made a timelapse sky animation I did suddenly change direction in the middle of the animation, very annoying.