Yep! I can remember Keon as a rookie and how exciting it was to watch a young player of his evident promise. There is no guarantee Marner will turn out to be like him, and, indeed, I would say that Marner is less promising defensively and more promising offensively than Keon. Though it is hard to say how much Keon's offense was restrained playing under an uber disciplined, defensive coach like Punch Imlach. But Keon did have a deadly backhand. The real comparison for me, however, is that Marner regularly makes me say, "Wow!" just as Keon did.
I think I may be the oldest poster on this board. I've been watching the Leafs a long time, have seen a lot of prospects disappoint, or only flourish after leaving the Leafs and am usually cautious about the development of young players. But Marner and Nylander are exciting in a way I haven't felt in a long time. The last time I felt this optimistic about a pair of Leaf prospects was when Sittler and McDonald were coming along.