I don't believe I've been over 80 mph. However, during a recent trip I really noticed the response when I "gunned" it a bit to pass. It was tremendous. My only point of reference is to my late 2000 Lincoln LS V6 which needless to say was not as powerful.
I took delivery of my MKZ in April, 2014. I have the complimentary maintenance. I have the 3.7L, V6 with AWD. My car will be low mileage, I currently I have 1343 miles. I plan on taking it in once a year unless there a problem.