bought my 159 2.4JTDm SW used (2006 ex demo and 1 owner) - it had about 15k on the clock
No issues when buying the car - car was faultless, dealer was great, good price, good p/x deal.
Since then I ahve upgraded the wheels to 19'' Ti alloys and Bridgestone RE050A tyres - I really like them, hide comfort still miles better than my old 156 and the handling is much better than when on the 17'' that came with the car.
Two niggles - still waiting for a B-pillar trim from the dealer and also just recently the clutch pedal has started to creak (only sometimes) - I don't think it is the clutch or clutch mechanism itself, feels more like the pedal moves a bit.
economy isn't the cars strong point - I am getting 30-32mpg from a full tank. Individual runs you can get 35-38mpg depending on driving conditions, traffic etc.
Comfort - faultless, I am 6'0'' my wife 5'0'' and both of us have no problems getting comfortable in the car and driving it. I have two small children and they are happy in the back in their child seats, plenty of room for them - they also sit higher in the car than in the old 156 so they can see out of the windows more.
Fit and finish - on mine still perfect, well screwed together, paint work swirl free and still (touch wood) free from major paint chips (the 156 had plenty
Gorgeous to look at inside and out, plenty of boot space for my needs and I still bring one and sometimes two buggies with me on trips with the children.
Engine is powerful and sounds great at higher revs. This is the first diesel I have owned and the torque is great, makes overtaking very safe
Negatives: wish mine had Blue&Me and electric memory seats and I want to get it remapped to make it pull from lower on the rev range and (perhaps) improve the economy. Oh and the tyres will cost me a fortune to replace but what the hell, I suffer from 19'' wheel vanity
Mine is Titanio Grigio, with Ti alloys, alu roof bars and black leather - it is in the 159 image thread that Fraser started.
I am extremely happy with the car and my wife is too, she fights me for the keys at the weekends and likes it when I take the train to work.
Buy one and enjoy