Not that bad for your first animation. I can't really point out anything that was too bad. You already seem to know the ins and outs of flash pretty well.
It was so well done that I thought it was making fun of "My-First-Submissions" to the portal haha!
I really enjoyed the character designs.
Did you do the voices for the movie, because they were done really well. I didn't notice any lip sync issues either.
I did, however, notice very few timing issues, but that can be fixed by just adding or removing frames. Most of those issues I noticed were in the main guy's (he looks like Steve from Blue's Clues hahaha) arms and hands. But thats really nothing to be that concerned about since it wasnt harming the animation in any way. I suppose it is just personal taste since I would have made them move and swing faster.
I also wish that there was a background. Nothing extravagant. Just a simple horizon line that is slightly darker than the background would do nicely.
all in all, really well done! I look forward to future submissions!