I'm trying to feel that way too... but the fact is there are people on the app engine team who could write SQL support for app engine in a few days in their spare time.

The problems with app engine and the datastore have shown that there was a high level misunderstanding underlying the core design of the datastore... and how it would function in the context of lots of simultaneous users.

So I'd feel a lot more confident if Google addressed this concern other than with the high availability datastore...