Here's the #1 question I have for any of these hosts, and I never see it answered: how stable is network throughput?

I run what amounts to a fancy real-time chat service. Are my users guaranteed a slice of the pipe? Do you have the resources to make sure they won't lag horribly if my neighbor is getting DDoSed?

Keep in mind that there is a difference between "we actively make sure you'll have a good experience" and "you happened to get provisioned on a machine with good neighbors", even though the anecdotes will be identical.