A new version of Guimup is available from sourceforge (source and 32bit deb package).
Version 0.3.0 was completely revised and rewritten for Gnome 3 and takes advantage of new feautures in MPD 0.16

guimup0303

DEPENDS: libmpdclient2 (>= 2.3), libsoup2.4-1 (>= 2.36), libgtkmm-3.0-1 (>= 3.2),
libunique-3.0-0 (>= 3.0.2)

Many new features and improvements. To mention a few:

* Implemented playing files that are NOT in the database:
“D&D” files from outside quimup on the playlist.
“Open with” from the file manager.
* Program now runs in single-instance-mode by default.
* New library mode: “Year” (i.e. date tag).
* New library mode: “Timestamp” (i.e. last-modified property).
* Replaygain mode can now be set on the fly from Quimup.
* Added option to ignore leading ‘the’ when sorting artists.
* Extended context menu for playlist operations (remove,
save, shuffle etc.)
* Separate button for all playback modes (repeat, single, etc.)
* More options, such as custom colors for the player window
and the use of ‘profiles’ to connect with mpd.
* Improved auto-detection of mpd’s settings (on localhost).