This is really beautiful. I'm using "Dawn" now, and I agree with the earlier poster who said it would make a pretty great default skin for MusicBee.
I do think the alternating row colors in the song list are a little too subtle right now. I have a glossy LCD laptop screen, and I can't even see them unless I look at my screen from an angle. The "Search" and "Panel Layout" toolbar buttons are also invisible for me, but I gather that's outside your control? I think the other buttons (e.g. New Tab, Back/Forward) are great, though. I like that the overall color scheme is simple and gets rid of unnecessary elements.
A few other (extremely) small quibbles:
- When the left sidebar is collapsed, the playlist-select button is a white triangle. It should probably be either black, or gray like the other toolbar buttons.
- The "up" arrow button on the main scrollbar seems to be a few pixels below the top edge of the column headers. The horizontal gradient also looks a little weird when the right toolbar is open. I'd probably make it a shade or two darker, rather than solid white.
- The corners of the tabs look a little thinner than the sides. They could use a little smoothing out.
Yes, I'm being a total nitpick here, but only because there's nothing else to criticize. It's a gorgeous skin through-and-through. :)