I haven't been following developments in the RoR community tightly, but I remember there was controversy over Dreamhost a while back. If you do a search I think you will find a post with DHH's response and a few with alternative recommendations.
Update: here it is -
The deal with shared hosts
I think you might be able to find a few more surrounding the issue
Also, I believe there's a new webhost that just went online 1-2 months ago offering total customisation? E.g. you could run Microsoft SQL Server + Linux on the same IP address or something like that.
There's been a lot of talk of how RoR doesn't seem to scale very well when it comes to deployment. What have you experienced about it so far?