I had a 2012 Grand Cherokee with all the off-road options before buying my JKUR a month ago, including the QDII rear diff.
I had taken it all over Colorado - Mosquito Pass, Kingston Peak, Mt. Antero, Hayden Pass, etc. I always enjoyed the looks I got from people in their lifted JKs.
The 4WD system was excellent, I never had any traction problems, and the full-time automatic locking rear diff was great. Ground clearance with the air suspension was great also - significantly better than the Rubicon actually because the front differential is not hanging out.
Reasons I sold it:
1) Ride quality sucked due to poor suspension travel and articulation, especially at higher ride heights.
2) Too much complicated gadgetry in the interior that I always worried about when banging around off-road. Squeaks and rattles from the panoramic sunroof, etc. Just a very complicated car.
3) Interior too nice - I don't want to worry about getting mud on the leather and wood trim.
4) Too much expensive painted trim near the ground, i.e. front and rear bumpers. Always had to worry about scratching them on rocks, shrubbery, etc. Also, as someone else mentioned, too wide for many trails.
5) When the power steering rack failed on a trail at 38,000 miles and cost $3,000 to replace, I began to worry about long-term reliability when used seriously off-road, and decided Wrangler was a better choice.
Also, I hit a deer last year, and discovered Jeep had placed the air suspension control valves right behind the passenger side front bumper. Deer cracked off one of the plastic connectors, leading to all air leaving the system, and the vehicle undrivable, resting on the bump stops with essentially zero ground clearance. Had this happened on the trail, I would have been screwed. As it was, needed a tow to the dealer and $3,000 to fix (luckily covered by insurance, unlike the steering rack).