I'm currently using capistrano, but it's feeling limited for my use case as I have to manage several "always running" servers plus hundreds of cpu intensive workers. Finding a good way to manage those workers across several cloud platforms and my own hardware has not been simple.
To be fair Deis already does a good job of this.
Then I can deploy with a single command?
I have done this a ton of times with Capistrano but it's always a pain in the ass for new projects because I need to install Nginx, PostgreSQL, RVM, Ruby version, etc etc etc. Lots of busywork I don't really care about.
It uses Heroku buildpacks to build self-contained containers with all your dependencies with one command: building containername
DO has a Dokku vm you can select when you spin up a new droplet.