Meh...
Personally, I think there is a portal hype, so I don't mind a portal video (as it's a great game), but there is too many 'Still Alive' music videos...
Now, the movie is made with motion and shape tweens, is it not? Some parts it works well, but at other parts it doesn't. For example, when the rocket turrent comes up, it comes up from the bottom of the screen, and you can see it before it reaches the hole. I suggest a mask, learn about it in the flash tutorial section...
The music was quiet and, during the beginning and the end, the black screen was too small, so you could see the white background...
Also, a portal can't kill, and a rocket turrent can't die, remember that now...
For a first flash movie, its ok and you have clearly worked hard, but probably won't be remembered for being something special, but I think the character drawings had potental, so with a bit more practice and a few more techniques (such as masking), you could make a pretty good flash...