I love this app. Simple, intuitive, just the right amount of functionality. Like a previous poster said, it reminds me of early versions of Winamp. Please, be very, very careful about adding any additional functionality. Please do not add useless crap like skins or any visualization junk. It's perfect, just as it is.

With that said, the only suggestion I'd have is the ability for the UI to be collapsed (similar to Winamp) into a very thin, horizontal box. As it is now, the player takes up a little too much screen real estate.

Overall, an excellent application!