So far it's really not too bad. The split second you let off the brake the engine starts so by the time your foot is even near the gas it's already running. I guess how much gas it saves depends on the type of driving you do, freeway driving like I do wouldn't help much but my wife is mostly driving around town so it could help there. Jeep hate aside, so far ( yha only 3 days) it seems like a good vehicle.
I did check out the fully loaded and then some $64,000 4 door Rubicon at the dealer and it did look pretty fun, but it's still not a Hummer.