The main attracting features of Songbird are: Cross-platform (available for Linux,Mac and Windows), Support for "Add-ons" similar to what you have in Firefox, and its ability to connect to iPod and other USB devices. But that's not all, it has features like library, skins (called feathers), flow control and mixing, CD burning etc. Some interesting features that you will not see in other media players are XUL rules ( yet another application of Mozilla's UI toolkit ) , multi-language (around 45+ supported now) and web browser with integrated search both for web and your local library. It also features a sleek mini mode as show below:
Well, if you are still not happy with the mini mode, you also have the feature to minimize it to system tray. To do this you have an Add-on. You even have notifications when a song starts! This feature startled me because, my media player lack this functionality. Right now we have less add-ons but I am sure you will get more as Songbird becomes popular because of the "developer ease" in building add-ons.
I have started using Songbird and dumbed Windows Media Player 11 because of many reasons: Its open source, there is good a look and feel, the features that have explained above. And to end with the Songbird team is giving away T-shirts (which costs!!) but you can always get a Songbird button from your blog or web site and showoff your support to this product.