Which Railshoster for a productive application in US?

Dear Receiver and Forummembers ;), I'm looking for a hoster in the US which provides the best enviroment for a Ruby on Rails application. This should include Managed Server Support by the Linux Administration (I have no experiences with Linux so far), Backup and monitoring. The load on the server will be around 200 active customers per day (so really less, but the need to be served quick)

Which hoster can you recommend? Which hoster do you use? Which hoster should not be used for such a project?

EngineYard. However if you can't afford that, RailsMachine is going to be the next best but the support is nowhere near the same level.