A few questions maybe some of you already know. What's the "instance" that is spun up...an LXC container? Also, is this only for Server or will also be available on the desktop Ubuntu? Cloud only or is this also for local use?
However, for development you can setup a "local" provider (http://askubuntu.com/questions/65359/how-do-i-configure-juju...) and deploy to your own machine using LXC. This makes development quick and affordable and makes it easy to test drive Juju without needing to use a cloud provider.