I know of one company that uses GoogleAppEngine in their project... (Along with PhoneGap)
A bigger disaster I have not seen in quite some time (two ill-suited products combined together)! Kind of reminds me of MS-CE.
They are now looking for another solution (after spending 8 million dollars in dev) - traditional SQL and native development (which was recommended in the first place but - some designers are more cleaver than others). It is gonna take many (hopeful) subscriptions to recoup the dev costs.
Good luck to them and you.