"Development" is so over played. You draft stars and they end up in the NHL. Domi, Horvat, Perry, Maata, Kahdri, etc, could have played in Peru, they would have made the NHL regardless.
Not all OHL 1st rounders pan out. The Knights have turned late O first rounders with a lot of question marks into legit NHLers/NHL prospects. Chris Tierney is looking like he could be one of the best Canadian forwards from the 2012 draft (after many had written him off after a poor rookie year). They took a chance on a 130-pound Mitch Marner in the late 1st and it's paying dividends.
Horvat, as a 9th overall pick in the O draft, was turned into a 9th overall pick in the NHL draft. Of the 8 guys picked ahead of him, only Ekblad and Nurse turned into higher NHL picks (and Horvat made the NHL before Nurse).
Then you have guys like Remi Elie, Kyle Platzer, Centorame, AA who turned into effective OHLers from late picks.
The Knights how to develop forwards. Don't think defenseman are developed as well but at least they know how to get talent into the program (Juolevi, Maatta, Zads, Tinordi).