I use exaile as a default audio player in my Ubuntu 10.10 Maverick Meerkat. I really like amarok but it is a KDE app and it does not blend well with Ubuntu. Exaile is much like amarok and I have been using it for sometime now. The multimedia keys do not work by default on exaile and must be enabled by activating a plugin. Just go to Edit>Preferences and click on plugins. Then check the box GNOME Multimedia Keys.
Now you can use your multimedia keys. Have fun.