Yet then you get into the trenches of it and (IMO) you realize the sum of its parts is much less then the value of the individual pieces. You feel the pain of the documentation writers who had to transcribe examples and helper libraries to ten languages, "beta" features that have been out for years, "examples coming soon" in README's that are two years old.
Want to use python3? That's cool, use the flexible environment. But it doesn't support taskqueues or many other features.
Need websockets? Thats cool, we kinda have this socket API and similar for some languages and environments. It doesn't really work in the flexible environment though sorry :X.
All our python examples are in framework X, that's sufficient for everyone using framework Y, right?
Don't get me wrong, my company uses GAE and its benefits outweigh the costs for us. But there is a very real "Googliness" to the failings of the platform. The shear breadth and requirements of "fixing" and iterating on GAE must not be a very fun project to work on.