Hey this is Matt from the Convox team. I'm happy to answer any questions about Grid (what it is, why we built it), Convox, or AWS/Docker in general.
I came across your guys' stuff about a month ago and was intrigued by the cedar stack of heroku being dockerized and started playing with it.
Immediately stopped when my simple hello world node app was 1.5GB in size.
Building a much more lightweight image for your node app shouldn't be too hard, though. Check out https://github.com/convox-examples/express for a simple example.