I just tried running Chicago Boss. I followed the quick start guide that had a lot of steps and managed to get a 404 error.
With Rails there are less steps: gem install rails && rails new path/to/your/new/application && cd path/to/your/new/application && rails server and you just point your browser to http://localhost:3000 and get a nice welcome page for your new skeleton app.
Chicago Boss could be improved in that respect.