I have over 25000 miles on this car and have yet to have a problem.
This car is the most reliable and unstoppable car that i have ever owned.
I live in NJ and have little country cottages up in upstate NY and going up those hills in a foot of snow and driving through the mud, sand, dirt, and grass has never posed a problem for my MKZ AWD.
The AWD system is so advanced sometimes i think it does better than my LR4.
The car is amazing in the bad weather and the engine is quite powerful.
It is not a rocketship but it's no slow poke either.
Very few people will use the AWD system like i do for example i went up dirt/mud covered roads yesterday but it is still a nice accessory to have.