Goggle bigtable support in DAL is already GAE specific. You can also access entities by id (which is returned after insert) or key using DAL. Mixing in native API is possible if needed too, as app portability is lost anyway with GAE. And the non web2py specific things such as N:N relations, debugging or profiling are already described in GAE documentation.
However, adding some extra information to the book would be useful. There is already section on GAE there, I see no reason why not to extend it. As you just started playing with it and you see the problems much better, maybe you should join the documentation team and add information as you go?
