First, great stuff, I think I remember seeing some of that reel a while back.
The first thing I would do is lose the "amateurish" footage, as it takes away from the polished content; that would bring the reel to a perfect lenght (you don't need the whole song either).
One minor thing on the intro. I would personally add a little motion to the zoom on the opening to give a more realistic feel. Maybe speed it up a bit as well. You know, that's all the rage these days.
Other than that, there's some very nice stuff in there.
I agree with Vince on these points, and I would add that overall there isn't really any theme in your reel. Not just in the sense that there is nothing visual tying it all together and making it more of a "package," but also in the sense that there is such a wide range of stuff that it's hard to get a sense of what your skills are.
If I were a client looking to hire you to produce a corporate video for example, I wouldn't know if there was anything here that shows you do that type of work, and that same example applies to any discipline that someone might hire you for. I guess what I'm saying is it MAY be beneficial to experiment with a new version of your reel that just focuses on the type of work you are typically hired to do. If that's corporate video, only show your corporate video work EVEN IF it's only 30 seconds long. That would be far preferable to a more scattered approach. Most people only want to see the work that represents what they need, and care little about the rest.
I agree on the lack of theme. If this is for corporate work, than stick to your more corporate shots/projects. I don't think most of the people that will actually pay for your services will have much interest in, or time to watch, yu personal, experimental work.
It's a bit long for my tastes as well. I don't think you should enslave yourself to the duration of a song, or x amount of its verses. A cohesive view of your work is important, the song isn't. And finally, I don't think "compostiting" is a real word.
Now that I've beat you up a bit, there is some really nice work in this demo, and the tracking work on the opening folder and the record albums is very tastefully done. I also agree that a zoom into the opening folder and a closer look at the video insert would add not only the oomph of motion but show off your tracking/compositing skills better.