I come to the Fusion Sport after having owned and driven, in order, 1999 Mustang Cobra, 2003 Mustang Cobra, 2005 Mazda RX8, 2011 Mustang GT, 2013 Mustang V6 Performance Package, and 2014 Fiesta ST. It is safe to say that the Fusion Sport does not fit into the mode of either the RWD cars I have had (2 or 3 of them were GREAT cars relative to contemporaries) or the Fiesta ST (which is the most fun car I have ever owned--not best, most fun).
In my experience, the Sport has very little if any tendency toward torque steer. It does not drive like a RWD car because when under acceleration, the thing just hunkers down and goes. You can watch the AWD system working in real time, and I have been a bit surprised about how often the rear wheels are engaged. It is more often than I expected. I have only a few times thought to myself while driving the car that I wish it was a more RWD-biased AWD setup. When accelerating through corners, it is possible to get the car going sideways, but then the stability control rears its head to keep it from getting too fun and/or unsafe. If driven in a hamfisted manner, the car will understeer, but even then not to the degree I have experienced in my mustangs before the were properly Koni'd and tired. Actually, the worst understeering car I had before changing dampers and tires was my RX8 of all cars. I believe that switching to a stiffer rear sway bar and adding camber to the front along with a good set of tires would make the Fusion Sport handle extremely well. There might be more room for improvements with struts and springs, but I have been pleasantly surprised really with the dampers that come with the car stock. I do wish the car had the option of the trick torque vectoring rear differential, but it doesn't.
If anything, the driving experience with the Fusion Sport, again in my opinion, is more hindered by the automatic transmission than anything else. When I put the accelerator down, I am never quite sure what I am going to get. (actually, I know I am going to get a good half-beat of nothingness to the point that when attacking a corner, you have to recalibrate when to get back onto the gas). At times, I get acceleration that literally challenges my old 2003 Cobra, at other times, the thing falls on its face. So, if I am going to complain, it would be more about the transmission, or maybe more accurately the transmission programming in conjunction with torque management that takes place at the engine. Apparently, there is a new transmission in the wings, and maybe it will address some of these concerns if it is ever put in a Fusion Sport. There might be ways to address this with a tune as well though I do not believe that I am going down that road.
I have been extremely happy at how nice the Fusion Sport is in terms of just being a car. It is probably the quietest car I have ever owned. It makes our Navigator sound like a truck (yes it is a truck). Sync 3 is not without glitches, but it is pretty darn good. And my growing children actually have room for their legs in the back seat. And the trunk, OMG the trunk.
Those are some Friday morning thoughts. The only way to know if you would like the car is to drive it. So, pretty much everything I have written here is moot. I would encourage you to take the time to drive it and then go visit an Audi dealer and drive an A6 3.0T. Compare the experiences and price tags. I was happily surprised when I did that. If they were the same money, I would own an Audi, but they aren't.