With large libraries, it is very helpful to be able to type the first letters of the artist you want to play, and have the library jump there. For example, if I wanted to listen to Coldplay, I would type "c", and this would take me to the first artist with the letter c. If I wanted to zone in closer to Coldplay, I could type "col". 

This functionality is different from a search bar, and I like to use both for different reasons. One reason would be if I only want to play one song by an artist, it is easier just to type the letter to get there, instead of searching, and then having to sweep the entry, and then research for a new artist. Most large wondows based players I have used, such as iTunes, winamp, and WMP have this functionality. It's nitpicky, but its one of those things you don't know was so important until its missing.  

Sorry about the length, and thank you!