I agree on the built-in gui editor, that is something I have always felt is missing in 3dgs...
I mean, we have SED, MED (with a skin editor too), WED, GED... we need a GUI-ED
Creating interfaces is just so slow and painfull. It would be great to have tool to just select the type of item and place them, to be able to see the iterface object layout and edit on the fly. Something like an extremely simplified editor to create UI's like Visual Studio's approach.