I thought I would reply just in case you were referring to the video that I linked to. If so, that is most certainly not a beginner's tutorial on the basics that one would need just to make a simple GUI!

Rather, it's the other end of the spectrum: an example of how the toolkit allows a large team to bring serious, large scale software engineering practices to bear on something ambitious and complex.

One of the great things about GWT is that it offers something to that entire spectrum.