Learning GUI programming with GTK+2 or GTK+3?

Question

I am new to GUI programming, and I haven't found yet what library is best for my purpose (i want to make desktop environment applications, eg. docks, panels, desklets etc.) I have started learning basics of GTK, mainly using PyGtk. Most tutorials i found on line are for GTK+2.0. Recently however, GTK+3 has been released. So i am a bit unsure as to what that means for my learning curve:

• Should i learn using GTK+3 and forget about GTK+2?
• Does using one or the other really makes a difference from the point of view of coding?
• Are there PyGTK bindings for GTK+3 already?
• Is there any available tutorial for GTK+3?

Since i'm new to this, i'm throwing myself into it blindly, but a bit of guidance may be wiser. So if you have any, you're welcome :)