One question though, what is going to be 'the cluster' (The site says it distributes work across 'the cluster')? Basically, will it be capable of interfacing with cloud API's or will it just be you manually setting up a group of instances to host the machines to run Docker on top of?
Never got in to Cloud Foundry because it's overly complex and very limiting. Always went with Heroku, but wished I could have a Heroku-style infrastructure on the above mentioned VPS providers for the benefits of running better hardware, being more affordable, being multi-region, etc, etc.
Digital Ocean: http://kencochrane.net/blog/2013/06/running-docker-on-digita...
Rackspace: http://kencochrane.net/blog/2013/05/running-docker-on-racksp...
Linode: http://stinemat.es (site seems to be down at the moment)
Don't see Linode listed there, but between that or Jclouds (http://jclouds.incubator.apache.org/documentation/reference/...) you have like a billion cloud API's available to you. I imagine teaming one/both would make Flynn a very interesting alternative to Cloud Foundry/etc.