So, the hunt is on amonsgt the perspicacious blogopuli to classify what kind of a thing Gmail is from a GUI perspective.
I haven't looked closely enough to comment but, since that never stopped me before, I'll comment anyway :-)
GMail looks to me like a classic bootstrap. I suspect that on the server side there is a model of the client side expressed in domain terms - concepts like inbox, e-mail composer, contacts list and so on.
When a client connects, it effectively downloads an implementation of that model. Once in situ, further conversations between client and server can go up a notch - expressed in terms of domain specific concepts "render the inbox will you? There's a good chap" rather than "At X,Y render a blue box...".
In my opinion, there is more power in that one idea than in the whole minatory miasma of WS-GetAGrip.