We run 45 server instances and handle ~20 requests per second on AppEngine. Like many others we run Jenkins to handle our build and deployment. Appengine is not perfect but we spend the majority of our time focused on delivering business logic software rather than backend / infrastructure / scaling solutions. This allows us to keep our team small and increases our revenue per employee. Our experience has been that many of the idiosyncrasies you deal when first starting with AppEngine make scaling far simpler down the track.