I thought it was interesting the maps used in the app are standard Apple MapKit controls; Yahoo decided not to use its own mapping service.
On a different note, aesthetically there is a 1 pixel purple line at the top of the app that really bugs me. I don’t have a clue why it’s there. The app icon is similarly awful, and doesn’t reflect the general prettiness of the app itself.
I don’t think the UI is stunning (as some have said, but it is decent — a lot better than what I expected Yahoo to create.