While I have yet to interact with the Liquid Web folks myself, I am working with a firm that serves its clients through Liquid Web.
They are an interesting hosting provider in that they own the facilities they operate. I'm not sure how significantly that impacts their service levels, but it definitely differentiates them from some of the competition.
I believe that there are other service providers that own their facilities, but its hard to know for certain. As far as competitors, I would venture to guess that Liquid Web competes with the following hosting providers:
I only wish they were located closer to the eastern coast!