Nice experimental flash
I think you synced the shapes very greatly with the music. Some parts weren't perfect, but it was overall very well done. The different colors and odd shapes were nice to look at. :) The only problem I noticed was that there seems to be some animation at the end without any music. I'm not sure if it's my computer or not but if it isn't you should have stopped the animation where the music stopped.
The lack of a preloader wasn't a problem for me due to the small file size. It's still not a bad idea to add one though. You can get some already made from Newgrounds and they're quite easy to add into your movie. If you still need help, people at the Flash forums wouldn't mind helping you. A replay button would also be nice.
Overall, I think this is a great first animation. With some more practice I'm sure you could make something really great (not that this is bad or anything :P). I wouldn't mind seeing more movies like this. :]