I used to have a 4 litre Grand Cherokee and the fuel economy towing the Hobby 635 I had at the time was about 7-8 mpg, maybe 10 on the best day. Day to day it gave about 12-14mpg. I'm told that the economy of the 4.7 motor is marginally better.
As a towcar it was more than adequate. I towed a Swift Conqueror and a Hobby 635 regularly as well as a host of other trailers. Stability was never an issue, nor was performance, but the auto'box has a tendency to change from overdrive to third at the slightest squeeze of the throttle pedalwhen the motor easily has the power to maintain speed in overdrive.
I actually rated its towing ability very highly. What I took exception to was the seemingly endless chain of catastrophic failures.