I converted into HTML Xclass tutorial and its URL is:
http://wwwinfo.cern.ch/~chytrace/xclasstut.html
It's not complete, but covers basics of programming with Xclass
library on which ROOT 2.0 GUI is based and I found it useful
for understanding example code of guitest.cxx distributed with ROOT 2.0.
Hope this helps untill complete documentation is available for ROOT GUI.
Regards
Radovan