Nothing!
This is the 5th Volvo Estate I have had. All have been previously owned. The highest mileage I had before moving on was in a 740 auto estate which had 225,000 miles and was still running OK!
The 850 is the best Volvo I have owned and quite different from its predecessors. At last a Volvo that doesn't need training wheels in order to go round corners. Engine sounds great and it has every creature comfort you can think of.
I've had my 850CD for 12 years since new. It's handled everything thrown at it including 2 growing kids and 2 dogs. It's cavernous for luggage and the only items replaced in 12 yrs and 103,000 miles are battery (2) brake pads, wiper blades (after 6 yrs!) and a sidelight bulb.
I've every intention of using another 103k on the clock rather than spend good money on another new-status car and get a bad purchase. Volvo got it right with this model. Very happy!