Dreamhost used to be bad, because of the amount of over-selling they did. They say that has been changed and are 'getting on top of things'. Their corporate blog, at
http://blog.dreamhost.com/, might offer the kind of info you seek. I haven't read it, so don't know for sure.
I am in the UK and must say that I am not over-enamoured with the speed of my sites at Dreamhost. And I seem to get some timeouts on a few occasions when surfing my sites. Might be me, I don't know, but at the price I pay, I can't really complain. I wouldn't put anything critical to my livelyhood there, though!
I also have virtual hosting at Colo-cation and Webair. I have no complaints with either of those.
Support - Colo-cation is top rate. Webair's isn't bad, but not as good.
Speed - For my two TGPs there; Webair is great. Colo-cation is not slow, but not as fast (for me).
Overall value for money, as far as I'm concerned, has to go with Webair, as they offer high bandwidth and space for less money.
To sum up... Use Dreamhost as a startup host, only because of the amount of space and bandwidth you get for your money. When your site gets more 'important' to you, move to a more 'trusted' host.
PS - By all means, if you want to test the speed of Dreamhost at (one of) my sites there, PM me.
PPS - If you want a money off code for Dreamhost, ask, and I will get you one.