Qmmp

It's not bad, definitely deserves more popularity. Winamp 2 skins support is a very cool feature, there's a decent number of other settings you'd typically expect from a good audio player. Some major downsides, however, are the lack of crossfeed (not crossfade) options and no encoder interface (aka converter).

Playback seems to stutter too at times, though increasing the buffer will help. On Windows, the volume can't be set if you use WASAPI output. You actually can enable software volume control, but that will lag, depending on your buffer settings.

There's still some good potential in this project. Would be nice to see it evolve even further.