As said, this is a very simplified player that has a playback engine of its own. But I don't think it actually has the capacity to be as powerful as to replace others such as Rhythmbox or Banshee for instance since because of the simplicity, the GUI lacks few things such as a playback progress bar for example (yikes!).
*. It supports the playback of OGG, MP3, WAV, AAC and FLAC file types.
*. Displays album-art (covers) if found.
*. Although not the most easiest thing to do using it but you can build playlists.
|Although while loading a folder that contained like 40-50 audio files, it did take sometime though...|
*. Audio volume gain support.
*. Supports plugins thus you can expand its features such as system tray support, export playlist to XML, etc.
You can install Muine in Ubuntu 11.04 Natty Narwhal by using the below command.
sudo apt-get install muine
And for other GNU/Linux distributions support, please visit this Muine home page for more.