I bought the 2004 LS Ultimate in October after having owned two previous Grand Marquis - the first was a 1988 LS purchased new, and the second was a 1987 LS purchased in 2002.
Having been used to the 1980's technology for almost 2 decades, I, as many new Grand Marquis owners here have stated, was surprised at the differences between the older cars and the new.
In another thread, someone complained about the harsh ride. My wife I and noticed this, too, and I chalked it up to the kind of suspension that today's drivers want. But let me tell you, the stiffer ride translates into much better handling. I'm able to turn into curves at higher speeds with no leaning, and even my passengers noticed the improvement.
With dual exhaust and 239 horsepower, this new car is a bolt of lightning at the starting gate. It is so much more refreshing than the 150 horsepower of the two older cars. I can accelerate out of trouble, if I choose, just as easily as braking out of trouble.
And those ABS brakes. Whoa. Early this week, when one lane of traffic was halted and I was passing in an adjacent lane, some jerk bolted out in front of me.

I slammed on the brakes, and the power assist feature applied full braking pressure. I expected to slide, with wheels locked, into the bogey. But I was almost literally stopping on a dime. My wife commented that it was a good thing that no one was tailgating me.
But, my wife and I are more accustomed to cruising with the speed control engaged. What a pleasant experience, the car tracks straight and true. Hills are not a problem; this car will step down one, even two gears to overcome gravity to maintain my selected speed.
The exhaust note. It sounds almost like a Mustang, although not as deep. Very satisfying sound.
I've got 2500 miles on it so far, and I am very pleased with every feature - except one. I am big and tall, and I have no room for my left foot. When I did the panic stop as mentioned above, I pressed the brake pedal down onto my left foot. It was painful. Ford needs to continue its R&D to provide more legroom for tall drivers.
That's it, no more complaints. The new Grand Marquis is much improved over the older models. I joined this forum in order to learn how other drivers are experiencing their new cars.
I hope to talk to all of you soon,
Charles