Sorry it has taken me so long to respond. For me, there were no significant increases in power or gas mileage; however, I think that the sound change was great. You could definitely hear a more throaty rumble when opening it up.
I knew going into it to not expect much on the performance end, but the purchase was worth it to me just for the aesthetics of the kit rather than the factory intake. But I'm one of those guys that likes the engine to look just as good as the outside of the jeep. They are fun to get dirty, but they clean up nice too. Ha.