They're actually really strict about getting the guys into the dark room right away if they are having symptoms. There are a few players, like Crosby that have had multiple concussions and they take every precaution with the slightest sign. Unfortunately, in minor leagues and in the NHL there are a lot of players that still play on with concussion symptoms, especially the ones that aren't star players... They only get maybe 8-10 mins a game and don't want to be off the ice, they're fighting to move up lines and a concussion, even once sets them back years.
It is moving in the right direction anyways... as long as players speak up about symptoms they are able to minimize damage.