My wife DD's her 08 2-door Sahara. She is a lead foot and gets 16 in town/20 highway. With that said, the 3.8 is such a wimp that even a leadfoot like she is can't get a ticket in it haha!
The only issues we have had is the hard top leaked at first(we have dual tops) They eventually got it fixed. We had problems at first with it not cranking, they fixed that. We have the lifetime powertrain warranty and I do all of the services myself since I'm a technician.
Pro's= reliable, lots of lift/aftermarket support.
Con's= not much power on road(great off road), keep the automatic cool and it will last(get it hot one time and its dead), rough ride, mediocre gas mileage(a XJ gets the same mileage with lots more power)
I would get the 3.8 again based on reliability. I know that the first year of the 3.6(pentastar) has some issues, mostly around the block not having all of the cast sand knocked out of it after the pouring process. This sand gets into the oil and thats not a good thing! The 3.7 that your GC has is a completely different motor from the 3.8, the 3.6 is a completely different motor from the 3.8. This is all a result of Chrysler changing ownership so much. I hear the 5.7 Hemi and the CRD is going to be available in the JK in 2014, maybe someone can verify.
I have a 09 Hemi Commander and love it! I will never regret getting the V-8 over the V-6