Songbird’s been garnering attention since its infancy, when it was billed as the open-source alternative to iTunes’ built-in music store. Songbird proposed to be an all-in-one music-meets-internet program, with store integration, podcasts, radio, &c.
Songbird is based on XULRunner, so it shares a lot of features (and code) with Firefox and Thunderbird. A quick look at the preferences screen, for instance, will immediately show the common functionality. A lot of it is simply configuration of Songbird’s network settings.
Songbird’s main interface doesn’t look a lot different than a lot of other players—Banshee, for instance—but here’s what I don’t get. Firefox and Thunderbird both have GTK bindings that allow them to render parts of the program with native-looking widgets. Songbird uses some strange GUI toolkit that looks completely out of place. It can be skinned with “feathers” (themes, basically), but never ever seems to approach anything resembling native widgets.
Like its XUL-based brethren, Songbird’s greatest strength probably comes from its flexible plugin architecture. They do everything from enabling Fairplay-restricted file playback to adding music stores and album art download sources. In this respect, Songbird has a technological advantage over its rivals; on the other hand, Songbird’s XULRunner core makes it slower than dog slobber, and I experienced this same slowness, regardless of platform, throughout most of the program development, from 0.1 to 1.0. Library access is painfully slow (even after it was relegated to a background process), and switching contexts invariably causes a delay.
In the good old days, the Linux version of Songbird used Gstreamer to play audio while the Windows version used VLC’s main library. The troubles of compiling GStreamer for Windows must have been resolved, since v1.0 saw GStreamer used platform-wide. This is not necessarily a good thing; my own thoughts on GStreamer are well-documented, but suffice it to say that despite its progress (even during the 0.10.x branch) it remains substandard compared to other renderers like Xine.
It should be obvious by now that Songbird does not, in fact, even belong in a GNOME Audio Play Shootout, since it has zero to do with either GNOME or the GTK+ toolkit.
In Summary: Songbird benefits from high extensibility, but its major drawbacks continue to be its inherent slowness (and bulkiness! ≈30MB download for Linux!) and what I perceive to be built-in ugliness with its widget choice. It’s very possibly that Songbird happens to serve your particular set of needs with playback requirements or store integration, but unless something very specific and compelling takes you to it, there are much better, faster, and nicer-looking players.