Cleanup is really an improtant step of animation. No matter how good your blocking is. If you don't cleanup your animation. It'll look like crap. In the book Thinking Animation, Mike Murphy said: "When I go in and do the nitty-gritty cleanup work, typically it takes 20 percent of my time to get to the point when it's cleanup time. Then the other 80 percent of my time is cleaning up."
In my last animation, my blocking was not that bad (of course it wasn't great!). But due to some lack of time, I didn't concentrate much on cleanup and I didn't clean up my animation the way I usually do. I went too fast (I had to!). The end result is CRAP!
So guys and gals, let this be a lesson to you. When you animate a scene, don't skip the cleanup phase! Its really an important step!