The engine is under powered for the amount of weight it has to pull around! Ford had packageing issues and thisis the only Ford V6 they could fit in it. It is basicly built on a Volvo platform. If you get the awd the weight goes up even more.
I do not have first hand experince with this 500 as a ford. I am guessing it should be stiff, quite and much more refined then previous fwd Ford platforms. The engine has a fairly good track record and has been used in a lot of Ford products. Ford's bigest area of concern is electrical it always has been. I had issues with my Fords and just about everyone I have ever known especialy wifes side has always had electrical issues.
My wife has an uncle that works for Ford so 1/2 of here family drive Fords because of the employee discount. The next big thing is powersteering pumps. None of the family have ever had a mechanical engine related problem or a transmission problems that I am aware of! They drive mostly SUV's, Vans and full size trucks. She does have an uncle with a Taurus not sure if it is a SHO or not but it has just under 200,000 and is still going strong.