Plainamp 0.2.1 has just been released. This is a major update. Among the new features:

• Playlist entry numbers
• Visualization toolbar
• Playback control toolbar

For further details please see the changelog. Also Plainamp is now bundled with in_mad and out_wave_gpl so it can play MP3 out of the box. The source code used to build these plugins can also be found at the files section.