I finally got to experience that! I guess I sort of knew what announcers were talking about when they said it, but now I know for sure. I went to a Boston Bruins game in January and a NY Ranger game in February. They were fun and I had a good time. Then last Wednesday I watched Detroit and Nashville duke it out for the #1 spot in the NHL (for now). All the announcers (radio, tv, etc) were saying that it was going to be a "playoff atmosphere." So I found out what they mean by that. Every guy on the ice is hustling for the puck, going into the corners, everytime a guy has the puck he is contested by the other team. You can tell it's more than just one of the 82 (?) regular season games. Every goal is a big one, every penalty (or powerplay) is a big one. I LOVED IT!!!
So I guess it's something you just have to experience to fully appreciate.