First let me tell you that I've been testing Ubuntu 11.04 Beta for a week now, and I really like Unity and the potential that it has.
Second, I love the Lenses and I think it would be really great if you include a Music Lens. I made a mockup with my idea here,
http://ubuntuone.com/p/mIU/ that shows songs, albums and artists, but it could include playlist and Ubuntu Music Store results.
Let me know what you think.
Regards.