It's really hard to catch and finish an alley-oop layup. At least with a dunk, you know that the motion is relatively simple. You're catching a ball in mid-air and coming down for the slam. With a layup, though, you're catching, coming down, and you have to shoot back up while you are falling. It's hard.
(Spoken like a true expert of hang time, I know).
Anyway, all this is to say that Dwyane Wade's one-handed alley-oop layup early in Game 5 of the 2012 NBA Finals was pretty impressive.