I really like the concept, but I would pick a song that far more upbeat. The pants need to dance more, they need more movement it looks kinds like forced dancing where it is now.
The badge, tag thing on the back of the pants is keyed out too, its really noticable. For keying to work you gotta be real careful about how you light it and what color you're keying out.
Check out my commercial, on the full res version you can see some of the background plate through the hand, especially on the first shot. Might not see it in this small version though.
When I lit the hand (my hand, and my friends can tell because of the hair on my arm) I had to make sure that there weren't any green highlights on it or it cut into the key. took a few tries but I eventually got something that worked okay.
nice... butt, I do agree that she needs to do a little more dancing. Alittle more shake & arching.. You could use maybe some better looking graphics in the background. Keying needs alittle work but overall its not bad.