Dreamhost is not worth it personally. I have many accounts with them, which I regret highly.
Media temple do have some very important and well known clients, but mosso seems smaller (10x smaller). MT also seem alot more advanced, and looks like they know what they are doing.
Check WHT (webhostingtalk.com) for a review on both.
Done some more research and I'd 100% say Media temple.
They are a tier 4 Datacentre.
