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