gtkmm 2.5.1 has been released
gtkmm 2.5 wraps new API in GTK+ 2.5, and is API/ABI-compatibile with gtkmm 2.4. The new API is unstable, until this become the API/ABI-stable gtkmm 2.6 when GTK+ 2.5 becomes the API-stable GTK+ 2.6.Read more