QMidiPlayer 0.6.2-2 beta is out! Find more about it here.
  This version has reached a fairly stable stage (in Linux) and has experimental Windows support. It has been the default midi player on my Debian sid for a few days.
  So the next big feature is visualization. It's progressing, too. Have a look at the picture below.

Primitive 3D MIDI visualization test

  It's still primitive, but it already has everything required to go mature -- tight timing, time stamp synchronization, etc.
  Well, I still hope that this tiny project can get into the official Debian repository... Is it a vain hope?