OK, here are some issues I've noted on 1.1.0-pre3. These probably go back to 1.0.x, too.
In the Playlist window, double clicking on the album art icon sometimes doesn't fill the media info for the current media, resulting in an empty information window. Right clicking on an item in the Playlist and selecting Information... seems to always work fine.
Selecting the album art download option in the Playlist seems to only affect the current playing media. For example, the album art for other songs in the same album won't be updated until you manually do the "Download album art" thing for those songs too.