Rails is well known for having good conventions and defaults. So it comes pre-configured with 3 common environments: development, test and production.
But I think that having a staging environment is also pretty common and a good default and I'd ask you to also include this environment by default.
Also, I'd like to suggest a change in the production.rb template:
# See everything in the log (default is :info)
# config.log_level = :debug
This shouldn't be commented. Here is the reason:
find . -name '*.rb' | xargs grep Rails.env.production | grep log
./railties/lib/rails/application/configuration.rb: @log_level ||= Rails.env.production? ? :info : :debug
So, if you decide to copy your production.rb settings to staging.rb you'll have a surprise when you see different logs.
Does it make sense?