This is what I remember.
Aside from the "I am very interested in your school" type of statement, he wrote a paragraph about why he was interested in each school. Not a sentence, but a paragraph.
In one case, for the school he ultimately chose, he talked about the academics and why he thought THAT school was for him and then went on to talk about a player he knew from that school and how much he admired him and something like 'if thats the type of person on your team, I want to be one of those.' He also talked about a personal connection he had to the pitching coach (he knew the previous pitching coach, attended a camp and knew someone who knew the pitching coach well, etc...).
With other schools, especially those that were farther away, he explained why they were of interest to him. He told them if he had ever been on their campus or attended a game and why those visits had drawn him to that school. In one case he explained how he had aunts, an uncle and a grandparent living near that university and how he would feel very comfortable there.
In case you think they don't really read these letters, I can tell you that as of a few years ago they most certainly did! I specifically remember one coach who visited our house...and we visited their campus (out of state), how that coach specifically referenced comments from the letter and from their questionnaire.
sandman - I'm not sure how to fully respond to your sample letter, but I would certainly see it as a form letter if it came to me. I really do not mean that as a criticism, I am just suggesting that a short paragraph with some of the types of things I mentioned above would be nice. No novels, just 2 or 3 'connectors' for your son to that school. Coaches do notice.