Product review (4 stars): Really moves some air!
I had the earlier version of this since the late 90's and just installed this one with 7" round ducting in my new home.  The previous installation of the similar fan used the 4x10 ducting - which, I'm not sure if due to poor ducting installation or the 4x10 ducting not being as efficient - this one seems to me to move a much greater volume of air and is just as quiet or quieter than the previous model.