Battery problems, though the fault was with a cheap Kwik-Fit battery; in other words I don't really blame the car.
One of the rear brakes jammed requiring a new caliper. Volvo agreed to pay half the cost.
The gas struts on the boot lid failed.
Other than that there was just routine stuff, so the car was pretty reliable.
This was, and is, my first Volvo. Before I test drove one I didn't think much of them, but compared to the BMW I had previously the 850 was very nice and very comfortable indeed. When I first got the car it was aged three with average mileage and it felt just like new. Today it is slightly over 10 and it still doesn't really feel or look much different. The leather seats are great, specially with children, and the built-in booster seat has been in daily use for all that time. The odd thing about this car was that ergonomically it felt right from the word go. Everything is where you expect it to be, and for the most part it just continues to work. Dealer service costs are high, but I get peace of mind. It is incredibly relaxing to drive on long journeys, and the amount of space helps to keep the family happy.
The engine can be a bit rough when pushed hard, but in general the 2.5 20v gives the car a reasonable turn of speed.
I enjoyed reading your review. Try finding a good, private mechanic. It can save you bushels of money instead of taking it to the dealership.