I disagree - do they still lock you to their db? if they do then you are going to have to do a lot of work if you want to move to a different platform
I've seen many Python apps that connect to a free MongoDB instance hosted on Mongolab.
(also worth noting that Node.js support for App Engine is currently in beta.)
(disclaimer: I work for Google on Cloud Platform)
Is this public? I have been waiting to hear this for ages! Great News.
I am planning a switch to node simply so I can run the same code on the front and back end. I was not looking forward to learning how to administer a server.