Bought the SE V6 in new. The v6 runs great and still does for me but I also do regular maintenance myself and change the oil every 3k on the dot. Keeping 34psi in all tires is so important for gas mileage as well. These cars can't and aren't made to be dogged and that is why people have rough shifting. It's all what you put into the car I just hit 200k and still have no issues with power loss, rough shifting and average 23mpg.
I purchased my 2006 ford fusion about 5 years ago with 60,000 miles on it. The car got me there and back a few places in Michigan. The only thing I have replaced on my car is tires, breaking, window regulator and oil changes. My check engine light comes on but i never had any problems with the car. The shifting in the car when it takes off fast because not coming to a complete stop it jumps or when it is cold. I have noticed that the 1st gear RPMs go to about 4 or 5 before shifting to 2nd. I have one slow oil leak that i have been putting Pennzoil high mileage oil in it to keep the leak slow. I changed the transmission fluid and it still seems to run the same. With Michigan weather good tires would be good to have but it gets through snow alright with cheap tires. The door handles are cheap and break and peal. My mileage now on my car is 135,000 and it still brings me there and back to different places in Michigan. It is a very good car that doesn't need much maintenance besides oil changes, tires and breaks. Very good car.
I bought this car at 34,000 in 2009. At the time I was a service technician and had to use my own car. Before the end of the 2 year mark I had put over 100,000 miles on this thing. I live in Ohio and drove this car to the Carolinas and Virginia beach annually, including a 24 hour straight drive to Texas and 24 hours straight back 3 days later and never felt worried about making it home. My point is, I beat up my vehicles and this has been a beast. AC failed around the 140,000 mark (didn't bother fixing it), I replaced the thermostat and drive belt at 150,000, at 210,000 the radiator and transmission cooler lines were replaced, driver side window regulator at 215,000 and now at 217,000 the transmission valve body needs to be replaced so I'm reluctantly trading it in before I press my luck any further. I can't talk much about labor cost because I do most of my own work, but replacement part costs aren't terrible (except the valve body). And even with the age of the car its still averaging 27mpg! My biggest cons are the cheap plastic door handles and the radio display has bad soldering causing it to blank out. Basically very minor things. Ford bought my favor back from GM with this car.
We bought ours brand new in 2006, it was a demo vehicle so it already had 3,000 miles on it, it is now 2015 and our car only has 80,000 miles on it, just had its first tune up, THESE FUSIONS NEED A TUNE UP BEFORE 100,000 MILES OTHERWISE SERIOUS PROBLEMS MAY OCCUR, we had friends who learned that the hard way. this car is only the 4-cylinder model but it doesn't seem as slow as everyone makes it out to be, and its been unbelievably reliable, only needed regular maintenance and a sense that had to be replaced at about 50,000 miles. Perfect midsized car.