I have an '06 Liberty CRD diesel. I have gotten 31-32 mpg on trips a few times. Most of the time the average mpg is 25-27. During the winter it dips to around 23-24 mpg. I live rural so most of that is on gravel roads and two lane highways with a little running in town.
Power wise, it is a workhorse. I have regularly pulled various trailers including a 300 gallon fuel wagon. all the trailers I have pulled have been both on road and off road on my farm.
It is not without a few quirks though. There is a lot of discussion here and at www.lostkjs.com
on little modifications here and there that Chrysler forgot to implement, but then, I have never seen a Jeep that hasn't cried out for a mod here or there to really make it a great vehicle.
The engine is very, very strong. It is a cast iron block with wet sleeve cylinder design, dual overhead cams, and a variable vane turbo. It is a solid design that has been used world wide for some time. Made by VM motori out of Italy. The EGR and CCV setup leaves a lot to be desired, but there are some workarounds that are inexpensive. The tranny is the 545 auto that is also on a lot of the V8 Chrysler products. There have been some that have had trouble with it, but I have never experienced a problem.
All in all, a solid vehicle even though only 11,000 were made for the '05 and '06 model years for the North American market. Europe and others have had it as an option for quite a while and still do. It appeared to be a test project by DC for North America. Getting your hands on one is pretty good shape might be a little difficult but they are out there.
If you like getting your hands dirty and turning a wrench now and then, they are a pleasure to work on.