Check out Steadfast. Their mid-west, so not exactly east, but their Premium Network rivals many of the networks on the east coast. Their support staff are also always friendly and helpful, and I think their offices are in the same building as their datacenter, so somebody will always be there.
We are planning to move some operations out to Peer 1 in LA (I know, not East Coast, but they have a very fast network between cities from what I understand). Evan has been working with Jim Brownfield and you can contact him at [email protected].
If New York is a consideration, check out RazorBlue. They are a managed provider with staff there pretty much anytime of the day. I am with them now and I have always been pleased with the knowledge of the techs and quality of the network. Dan's email is dkitchen[at]razorblue.com. If Chicago is a consider, I would definitely look at Steadfast Networks. I am client there now as well and I consider it to me one of the best for gaming and other low latency applications.