My wife and I love our KK too! We have an '08 without the sky slider, but I just got a roof basket to stick up there, and I am very happy with that. The seats are extremely comfortable, so it rocks on a long trip. It's a good vehicle to drive if you have a bad back. If the KK you're looking at has a plain old sunroof, check to make sure there are no headliner stains. Some people have posted lately that their sunroofs are leaking, and it seems to be a recurring problem on certain vehicles.
Here is a site where you can paste in the VIN and get a factory build sheet for free (as long as you don't do it too often):
http://www.compnine.com/vid.php?. I used this when looking for my KK because dealers don't often list if a used Jeep has CommandTrac (4 wheel LOCK) or SelecTrac (4 Wheel AUTO). The SelecTrac is the rarer option and it allows you to have the 4WD on all the time if you want to. The CommandTrac is part time 4WD, for when you are on slippery or rough terrain. I have the CommandTrac. Other things you can see on the factory build sheet include special packages that include Cruise Control and Fog Lamps, the Skid Plate package, Full Sized Spare Tire, and the Towing package. All good to have if you can get them!
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2008 Liberty Sport 4x4 Automatic
Jeepin By Al 4" Lift Kit
BFG KO2’s 245/75R16
Full MOPAR skid plates
Rock Lizard Skink Super Sliders
AtTheHelm Front Recovery System & Roof RackM116A3 Trailer build thread: viewtopic.php?f=72&t=77997