PyGTK is unmaintained and has been archived. It has been superseded by PyGObject. Links below might not work anymore and information below might be incorrect.
New features from GTK+ 2.12:
Updates to Pango 1.16 and Atk+ 2.12
GtkToolTips.tips_data_list will now always return an empty list. New wrappers for GtkImage constructors
Much improved garbage collection integration using PyGObject 2.12.x which makes PyGTK applications use less memory
Many code generator improvements.