Had an '02 2.0 JTS Sportwagon a few years ago and thoroughly enjoyed it. Never had any major problems with it for the 2 years I owned it other than the airbag warning light and engine management - which were both repaired under warranty. ( the car was a year old when I got it ) It did like to sup the oil though!
I now have a 2.0JTS GT. Had it for about a year now with no problems whatsoever.
Test drove the 1.9 JTD and JTS to compare and preferred the JTS. Found that the JTD ran out of revs too quickly. However, torque and acceleration were very impressive. As is the fuel economy.
I also probably went for the JTS over the JTD as I had experience with the same engine before.
The GT is a great car to own; superb styling, awsome handling, decent acceleration, good economy ( +/- 30mpg ).
I must say I preferred the dash in the 156 compared to the GT, which is lifted straight out of the 147. Though it is still well laid out and solidly put together. The red backlights on the dials are superb at night.
Front seats are extremely comfortable - go for the leather option if you can - the Alfatex tends to shine up over time.
The back seats sit two adults comfortably, if under 6feet tall. Access to the back seats is not the best but adequate.
Rear visibilty is a bit restricted, so try to find one with rear parking sensors.
The surprising aspect of the GT is the boot volume.
The rear hatch hinges at the roofline, unlike other coupes which hinge at the bottom of the rear window.
This gives the GT superb access and carrying capacity.
I've just had the CAM belt service done, so hopefully should have a few more years of happy motoring ahead.
If you have any more specific questions drop me a line.