We are using the Google Cloud Datastore for quite some time at Blossom.io (through App Engine) and it is an amazing piece of technology.

Since scaling the data-tier is the most challenging part of building a high traffic application (especially when it comes to scaling writes) the Google Cloud Datastore (& App Engine) imho is among the very few services that can actually claim to solve this problem whereas other platforms just try to market theirs this way – "go cloud and then you can scale automatically (if you know what you do)".

I'm really glad the Datastore is now also available outside of App Engine.