I love my 850. It is my first car that my family has owned since 1997. Four years ago when I started driving it I was admittedly ashamed to have a "soccer mom car". My attitude quickly changed. Its a N/A four speed automatic that is going on 274000 miles. The car is showing its age with little squeaks and rattles, the hatch no longer stays open on its own, and little bits and bobs seem to be wearing out. Despite this it has been an incredibly safe form of transportation. While repairs are far from cheap, the engine and transmission are bulletproof and continue to work well, and I tend to push this wagon very hard.
The interior space and comfort is the best thing about this wagon. I call it my front-wheel-drive pick up truck because when the seats are folded down you realize how cavernous this car can be. The seats are the most comfortable I have ever sat in and road trips are a breeze.
Do yourself a favor and buy a manual. The automatic is quite sluggish and not very efficient. If you can't drive stick, make sure to get one with the sport switch which lets you more easily access the higher RPM's.
I bought my 850 used, the previous owner beat the crap out of it and I've been restoring it. My 850 lacks the turbo, it is a bit slow. However, the 5 cyl engine that Volvo used in this car is rock solid, it starts every time.
The car drives like a dream, it holds just about anything you can imagine, the MPG is nothing to write home about (avg 19.8 MPG). The gear shifter is a little notchy, requires a large throw. The odometer stopped working at 185k miles, but using the computer diag port, it's actually got 214k miles - the vehicle shows no sign of giving out - it just keeps going! The suspension and all wheel disc brakes give it a sporty edge, but the engine is under powered.
The climate control is a little weird, but it works well enough. The turning radius is crazy awesome, the brakes are great.
Wish the electronic seat was more reliable, wish the 5-speed manual came with a turbo.
I bought my car with 105,000 miles on it as the fourth owner. I had it for a year. It was awesome as a college student to be able to haul around my friends and my stuff. However, previous owners had not cared for the car properly and I ended up with a blown piston ring after a year of ownership. That pretty much totaled the car ($3k of repairs for a $3k car) unfortunately. However, I bought a used 2002 XC70 because I loved my 850 so much. It was taken on several car trips (camping, skiing and paintball) and performed well in all areas. I wish I could have bought another. Be aware when buying used- if the person before you hasn't done the maintenance, the car will fail.
Sunroof, 3rd seat, individual reading lights over the rear seats (perfect for friends to read or do homework on long car trips), window controls in middle console, dual climate control.
Cupholders! This is the primary complaint from 850 owners- there is only one cupholder that is actually useful and they are placed in such a way as to seriously cause harm to the electronic window controls.