Have personally used RailsPlayground myself, although not the VPS.
Support's really on the ball. With loadtimes, uptime etc never been a
problem yet. 5 Star's for Rails 
OCS never responded to a generic query when I was hunting down remote
hosting locations some time ago.
Ultimately, depends on the job it's for.
Don't play on the train tracks too much, GF's tend to ... Well enough
said
J