Similar to my suggestion for File/Folder, the ability to filter by the "Album Artist" metadata tag would be a massive help in my collection. I have many, many albums that are "compilation" or mix albums that are comprised of works by various artists. Sometimes, I really want to listen to a TON of dark Drum & Bass or Neurofunk, so on my desktop player (Tuniac) I'll filter by Black Sun Empire. This will give me all the albums that BSE produced/released even though individual tracks on these various albums may be by other artists. This also makes it much easier for me with things like record labels, such as Liquicity Records. They release tons of compilations and other artist releases under their banner, and they're all typically of some sort of liquid drum & bass. Instead of having to know each album or artist individually, I can search for Liquicity as the Album Artist and I'll get almost all of my liquid DNB in one go. Same goes for things like ATB's wonderful "DJ in the mix" series, or the "Sunset Beach DJ Session" series, etc.

Firefox OS is not being worked on