One misconception that popped up during the Mariners' weekend series with Colorado in Coors Field is that the Rockies' usage of a humidor completely negates the offense-happy conditions of Coors Field and that Coors Field is now a more typical playing environment.
While the humidor did cut down on the number of home runs, Coors still has an unusually large outfield, which gives outfielders more ground to cover and is an advantage for hitters, since chances are more likely a ball hit to the outfield will drop in.
Also, the Mariners broadcast team on FSN discussed this during the weekend's games, since they got to tour the humidor: The humidor doesn't weigh the balls down to counteract the high altitude. It simply maintains the temperature and humidity of normal conditions. Denver's climate dried out baseballs, which exacerbated the high altitude's effect on the ball's flight. That high altitude effect still remains to some degree.
Notice that the Rockies, as a team, still hit very well, and their pitchers still tend to sport higher ERAs.