I don't know. Very inexperienced. Last season they lost seven games in a row and he needed to call in the help of Dick Advocaat as adviser. He doesn't seem like the most gifted tactical manager either (Advocaat f.e. said how easy it was too dismantle Feyenoord when they played Fenerbachce in Europe). He also seems like a very mellow person. Too mellow for this high profile job maybe (english press mostly)? I don't know him personnally, I could be wrong about that. Feyenoord is a big job too, but as a kid of the club he has more credit with the fans etc.
Wouldn't mind giving him a chance though in a couple of years, very likeable guy. Not a particulary good argument to want someone, but still .