I own an 06 Grand Cherokee with the om642.
Mine is the overland spec with Quadra drive 2 , which basically means it will go anywhere... just had some snow here in the Uk , not much of it about 4 inches which froze and left the roads a bit icy but the Jeep just pulls away on solid ice without even any wheel spin its just stopping when it gets tricky same as any other vehicle.

I get 22-25 Uk mpg in the cold weather and a constant 25 overall in warmer weather and can have about 28mpg on motorway runs. Our gallon is 4.56 litres.
0-60 is just under nine seconds and the om642 is quicker off the mark and overall than the 5.7 hemi version
I run mine on home made biodiesel.
I wanted either the ml or e class or the Jeep and settled on the Jeep due to ease of working on it with no need to lift it to get underneath and removing the plastic arch liners gives great access to the sides of the engine.
Its only geared for 120mph hence the low fuel consumption, the e class gets around 40mpg I believe.
I came from a w210 to the Jeep so getting used to sitting higher and getting rocked about sometimes on potholes took a bit of getting used to, w210 had gearbox tunnel and door to sort of brace yourself against where the Jeep doesn't and the Jeep does not have a ‘dead pedal’ to rest your foot on and being 6’4” I find the armrest low so have a after market raised foam filled one on top of it which is about 4 inches high.

It is my first AWD vehicle and its a hoot to drive , just point it where you want it to go and put the power on and off it goes, no wheel spin apart from a slight chirp as it launches.