I think the biggest thing to me was the song. It was fine until it got all rocky and then just ended abruptly. I almost had to turn down my volume. I've heard in some cases, employers looking at demo-reels will just mute the sound, it's not important to what's being showcased. That said, if you're going to have sound, make it somewhat enjoyable and easy to listen to so the person who is watching the reel doesn't feel too distracted by it, which I honestly felt at the end.
Also, everything that Brad said. I will add though, my 3D instructor, whom I have much respect for, advised me to structure my reel so that my best work is the first thing that comes up. You have only a few seconds to impress someone before they either stop the video and move on or decided to continue watching. Put your best work at the beginning. Your second best piece (or something that's equally good) should be at the end. End it on a good note so they remember something good. Everything else goes in the middle. That said though, its always good to have good work all around.
You can see the reel I did for class here: http://scottgrasso.org/
. It's nothing spectacular as I spent most of my time working on the car and lost a lot of better modeling work during a hard drive crash. Much like your reel, if I had better content overall, the reel would be much stronger.