Haven't seen much of Cillessen but it would only be natural for us to feel a bit disappointed at shifting from DDG to someone with a less than world class reputation. He may well prove to be good enough but as is I'd worry that we'll see the return of our old GK problems....
My confidence in LVG's opinion on goalkeepers was not enhanced by him saying he had initially been unsure on De Gea either. Given how outstanding DDG obviously is, that's less than promising....
In my opinion de gea is a good 2-3 levels above what he was a year back. A year back he was a good keeper but now he is maybe the best in the world. I think frans hoek has a not so insignificant role in this transformation.