The Maxima is a very good car too, but for some reason it just hasn't been able to be competitive, not for lack of merit, its just not. As for your friend's Accord, every carmaker has their foibles, but if you look at the JD Power IQS ratings, you'll see the Camry and Accord are ranked much higher than the Taurus, as well as in the long term dependability studies. There's no question that in the big picture, less Camrys and Accords are in the shop than Tauruses.
As for the DVD Navigation systems, when I bought my Lexus in 1998 I drove one with the nav, Lexus' first, had no interest in it, so I didnt get it. After driving the new ones now, I wouldn't buy another car without one. Its so convenient, you're sitting in traffic wondering, will that exit get me home? Well hit the home button and bam, the nav system computes a course from your exact position. No more fumbling with maps, no more stupid mapquest printouts to annoy you when driving they're the way of the future.
As for the DVD entertainment systems, ever been on a roadtrip with two 5 year olds? Don't, unless you have a DVD entertainment system
Its the way of the future, these new niceties from luxury cars are starting to trickle down to mainstream vehicles, and if Ford doesn't up their offering in the Taurus, its going to be wounded forever.
In order to remain competitive, you MUST be open to change. Ford has trouble with that, as does GM.