I currently have 3 Thunderbirds: '56 Peacock blue, '66 428 Tahoe Turquoise, and '04 Merlot.
I had a '96 Tbird that I didn't keep long. It was a v/8 loaded. It did not have a limited slip rear end, and even when it rained, the right rear wheel would spin, and you had little traction, so if you get one, I would not get one without "posi". I had a lot of trouble with wheel balance issues. I went through 4 sets of tires and 2 sets of wheels, and no one, including Ford could figure out why I had balance problems at highway speeds. I traded it in with 11,000 miles on it for a Black '98 GT coupe, which I traded in with 2,600 miles in 2000 for a Black GT Convertible, which I traded in with 5,000 miles for a 2004 Tbird.
I had a friend at work who also had a '96 Bird, and he drove his for about 150,000 miles before it finally was shot. As for the person who commented about loving the new birds, with an SCT tune, K&N CAI, and glass packs, I would guess mine to be putting out about 320 hp, and it really moves.
I also have an '08 GT vapor coupe now with about 2,300 miles on it. I changed the plugs to the one piece Champions, and have been getting unbelievable mileage. On a recent trip to Wisconsin, at the speed limit, no air on, with cruise set at 65, it got 30.3. Right now just driving to work and back this week, it's at 25.4, and that's with an auto.
The highest I got before the plug change was 27.1, so the plugs must have had some influence on the mileage.