I had the same experience, important because the spouse has a desktop and a laptop she uses on the first floor connected wirelessly. Simply replacing the router gave me a similar boost in wireless speeds at these two different locations.
My laptop is 40-50 feet away from my router and down one floor. The new router is in exactly the same place as the old one. I am consistently getting 60-75 mps download. the best I got with the Rev. F was 35-40.