I have to use rental cars all the time, and I must say that the Jeep Liberty is the easiest to hardwire. I "hardwired" (actually, it is still in the cig lighter, but it is tucked in so that the wire is invisible) it today for my trip tomorrow. I will have to travel for about an hour in VA and didn't want wires hanging. I have my own 10' custom straight cord for this purpose.
Anyways, It was very easy to stick the wire between the glass and dashboard, ran it up the window frame which had a space between the plastic and the metal frame, and then the roof lining which had about 1/8" space.
Man, I am not sure if I ever want to own one. it has no power, but you get up to 90 thinking you are going 55-60.