I signed with Scribe Agency in mid June, so I can add a little more to the pie -- not much, but for the curious:
Years ago, Kristopher O'Higgins did some work with Tor books -- in editing, as CaoPaux pointed out. In fact, there's a great story about how, years after he left, he sought out the author of one of the manuscripts he was unable to buy and offered the fellow representation.
Kristopher and Jesse currently represent about half a dozen clients (that number depending on whether or not everyone's signed everything they were supposed to within the last month or so). They're terrific guys, and their answers to my questions are making short work of my naivete.
Darin C. Bradley