Throttle response is a little better. Can't comment on the mileage, I drive in the city and mostly short distances or get stuck in traffic so I don't get any if I try (19 mpg on a good week, 15 on a bad one) Still can get 28 on the highways though.
You can hear the sucking sound of air when the throttle body opens up. Also you get a nice sucking sound when the car's cold. When it warms up it does go away though.