I've heard mixed reviews about the noise level of the InSinkerator Badger 5 1/2hp. How loud is it during operation, and does it affect your kitchen environment significantly?

As far as garbage disposals go, the Badger 5 isn't the quietest. But it's not really louder than any of the models in the same price range. Generally, unless you run yours for minutes on end, which is not recommended, the noise won't last long enough to irritate.