TBH, the UI is a bit of a turn-off. It makes UKMP's look good (which I still think is a bit bare bones).

It's little things like having graduations scroll as well as items, but then not line up; elements without a visible bounding box or button (e.g. the "OK") etc.

Short version: look at iTunes, the iPhone or Canola (but keep the album art in the listing view, which hopefully the next version of Canola will get).

Long version: I'm not a good UI designer; I just know what's usable when I see it