Just went from a 2008 Sahara (6-speed) to a 2012 Sahara (auto). Unbelievable difference. The 3.6 kicks the 3.8's butt.
I pull a 1850# pop-up camper and when running eastbound on I-70 from the Vail area to the Eisenhower Tunnel (Continental Divide) the '08 was a constant 2nd to 3rd back to 2nd and only maintaining 25-30 mph. The '12 maintained 50-55 mph and only dropped down to 3rd.
Ride is much refined (yeah I know it is a Jeep) and considerably more comfortable since it is the daily driver. Only thing that I would have down without is the painted roof. But it is black over black so it works well (doesn't look like an H2).