Most 7th rounders never play a single game in the NHL, so this one is already above the curve. This is a good signing, even if he is just competition at training camp.
Now if (unlike Hextall) Dubas actually calls him up to the NHL sometime, and if Sullivan actually gives him minutes, maybe we can really see if Puustinen is an NHL player or not. Puustinen's never going to be mistaken for Teemu Selanne. But he might have the tools to be an NHL regular, or at least a bottom six fill-in player.