If you like the way the car looks and drives and can find one with relatively low miles, that has been maintained and hasn't been too abused, go for it. I'm happy that I did. The S Type from 2003 on has an improved drive train, interior, and reliability. Stay on top of leaks and maintenance and it should hold up fine. The car drives super smooth and with the NA 4.2 V8 is pretty quick. If you want to have the most elegant car at the drag strip go for the R model, if you don't like to drive fast a V6 model is the most plentiful and still has 240 HP for passing other cars. Ford has made Jaguar a better car and much more reliable than the ones from the 80's and 90's, going from the bottom of the reliability lists to the top. With the rear seats folded down there is a lot of storage in back, making it practical too. Don't use the car for carrying gravel or firewood though, the car is too dignified for that. Because most people think that a Jaguar is going to explode at any moment they are a bargain for what you get too.
I bought my car in 2005 with 10k miles on it. It is my all the time car and now has 97k miles on it. The only problems I have had is the front driver side barren went out, replaced the brakes twice, and the electronic e-brake went out (which I have not replace). I do not considered these major problems. I love this car and complete recommend it to any one. I do not plan on replacing it anytime soon. I have been through 2 major accidents and have never been hurt. The car still rides smooth and if you look at it you would never know it has been through the accidents.
The clock needs to be easier to set. I gave up on changing it for daylight savings time. I love my Jag. My son bought it when he got out of the Navy. One month later he said he was going to trade it in. That it was an old man's car. I told him I would give him my 2002 Chevrolet Impala that was paid for and I would take over the Jag. I got the better deal.
Bought the car new. The interior is made cheaply and has flaws. The headliner fell down after a few years and is expensive to replace. The vanity mirrors have covers that break off easily. The cigarette lighter works some of the time. The clock and radio require the manual to reset as it is not easy to remember.