In terms of serve. He gets alot of aces and winners but it seems its mostly from guile and disguise. Most of his aces are the result of the opponent being completley fooled and leave them frozen. OTOH, if they get a racket on the ball, they can usually hit a decent return. In the past, Fed could also overpower people with pace and force alot of returns long. It reminds me alot of Mcenroe's service games later in his career when returners were essentially just guessing which serve would be coming and he would either get the easy put away or get passed by a brutal passing shot.