The 4.0L certainly has it's perks, but it's shortcomings more than made up for them. While the only place that my '01 has any signs of leaking are at the back of the valve cover gasket, that's easily fixable, and any of the garden variety oil leaks can be handled without much trouble (not that there aren't exceptions.) Sure, I love my 4.0L, but if Chrysler had more money back in the 90's and less fanboy enthusiasm, I think the 'ole straight six would have been axed a lot sooner. It's overweight, the low-end torques kicks in about 300 RPM too high for my taste, and by the time mine was built, a number of annoyingly disparaging ideas were thrown at (I looking at you restricted manifold ports and coil rail.) I don't care much for the glorified minivan motor that is the 3.8L either, but between government emissions controls and the cost effectiveness of using similar parts (like engines) across multiple platforms, Chrysler/Fiat will end up making Jeep more and more generic. Sadly, there's nothing we can do about it, because Chrysler is making their money off the people who want the look of a Jeep without caring about the little things like capability, adaptability, and reliability.
"Some Assembly Required" is a target, not a deterrent.