How will this work? It sounded like a user could just build a custom VM image and send it to you. There wouldn't be a way to deploy that to heroku, right?

Are you doing sort of a blended app hosting/cloud offering?

With what we have today, code on our pre-configured RoR stack will work on heroku.

What we have in the works is detecting if you have e.g. Redis and subscribing to that "addon" for you.

Have you seen the dotcloud "build files" for specifying services? I wonder if trying to encourage standardization among cloud/app hosts on a service specification file like this would be beneficial, similar to Gemfile/Procfile/etc.

service 'redis', '~> 2.2.2'

http://docs.dotcloud.com/guides/build-file/

dotCloud team here. If there's interest, we'll happily contribute our specs and code to get things started.

I'd love to. I'll email you soon.

I smiled reading this exchange, very good-spirited. Hope you can successfully work together!