There are new tools[1] being built around Docker that make it viable to easily move your apps out of Heroku and onto any system running Docker including DigitalOcean, GCE, AWS, etc.
When you combine Docker, buildpacks, and CoreOS[2], you get a scalable and flexible platform that you can run anywhere. It has taken people a long time to combine the simplicity of Heroku with the flexibility of bare metal, but the open source guys have finally put all the building blocks together.
Another tool that does just this would be Deis[1]. We specifically combine CoreOS (in heavy development[2]), Docker, Heroku Buildpacks, and also Dockerfile deployments[3], too!
