Working with the Mac OS X port of Gedit, version 3.13.91
  ftp://ftp.gnome.org/pub/GNOME/binaries/mac/gedit/beta/Gedit-3.13.91-dbg-1.dmg

When Gedit is quit when a document has unsaved changes, the 'save document' prompt comes up. Cool. However, clicking on 'Save' (or 'Save as...' if the document has not been saved before) saves the document but no longer quits. Sniff.

0) Install Gedit beta on Mac OS X
1) double click on the gedit icon
=> Gedit opens with a blank document
2) type 'Gedit is cool'
3) call 'quit' (e.g. with menu entry Gedit > Quit)
=> A dialog window opens with 
    [Close without saving] [Cancel] [Save as...]
4) click 'Save as...'
5) change name to 'temp'
6) click 'Save' in dialog
=> file is saved but GEDIT DOES NOT QUIT


A similar thing happens with a document which has been saved so already has a name but which has unsaved changes
0) as above
1) ibid
2) ibid
3) save to 'temp'
4) type ' but won't save and quit'
5) call 'quit' (e.g. with menu entry Gedit > Quit)
=> a dialog window opens with 
    [Close without saving] [Cancel] [Save]
6) click [Save]
=> document is saved but GEDIT DOES NOT QUIT

cheers.