For example, when the active source is a DAP, and tracks are beeing imported, the are not displayed in the PlaylistView. The user has to click on another source and then click back on the DAP source to see al th tracks.

I think there a re different problems, but I have not been able to fix it completely:
* in PlayerInterface, RaiseUpdate is not used when adding tack
playlistModel.AddTrack(args.Track, true); instead of playlistModel.AddTrack(args.Track;

* PlaylistView: does not listen to model.Updated. A brief summary of the hanged I made:
this.DrawEnd += new EventHandler(OnDrawEnd);
[...]
void OnModelUpdated(object sender, EventArgs e)
{
  if (this.drawing == false)
  {
    this.drawing = true;
    this.ThreadedQueueDraw();
  }
}

* DapDevice does not call source.OnUpdate when adding track:
public virtual void AddTrack(TrackInfo track)
{
...
  source.OnTrackAdded(track);
}

With these changes, the PlaylistView get filled in real time, but only until the scrollbar appears. Then, it stops updating the list of tracks.