I'm absolutely against this piped-in noise.
1) The sounds of hockey are right up there with the crack of a bat crushing a 'tater, and two combatants battling it out in front of a silent crowd on the grass court, as the best sounds in all of sports (honorable mention horseracing and F1). More of that please. Just add the extra six seconds of tape delay to bleep out all the cursing.
2) No one can live-mix the artificial reaction of a crowd during a playoff hockey game. Unlike the many seconds it takes to develop say, a dramatic field goal kick, or the roar of approval after a 37' putt, hockey hits, goals, etc happen in the blink of an eye. It's gonna be like watching a half-empty stadium of new hockey fans try to figure out what hybrid icing means. Lots of half-energy.
3) We all love players being mic'd up; with such a small area and so many passionate men it's an insiders dream. Hearing players and coaches yell for line changes, chirp at the refs, encourage their teammates and celebrate goals is way cool.
This is of course disregarding the effect on the players, but from a tv fan's perspective the extra space to set up cool cameras and hear all the cool interactions seem awesome for a small series of games.