I think that a recruiting service can be beneficial when the kid is not a stud, maybe just good and has money to spend. A guy from Diamond College Advisory (Justin Cronk, played football and baseball at Amherst) has spoken at our school. He is supposed to have a pretty good handle on the academic schools and a few others. Part of his pitch is that he knows, for example, if Middlebury needs a SS or Williams has a certain need in a certain class and how likely a recruit is to play four years, or three etc. Some folks from the school have used him and are happy with the result. We will not use him and I have no connection with him, this is just FYI.
edited to add link: http://www.diamondcollegeadvisory.com/who-are-we.php