They are like any modern car made by any other normal
car company. They are good reliable quite efficient cars
if they have been well and completely maintained. They
are pinless hand-grenades if they have not been properly
maintained.

Older volvos are absurdly over-engineered. While they
aren't exactly reliable, they are extremely durable.
What this means is that they can be abused and abused and
then when something breaks you can fix that and maybe
a couple other things and have a car that is pretty much
good to go until something else breaks. Oh,and they are
reliable if you do keep up with the maintanence and also
fix the couple of manufacturing defects that are common to
all of them (rotten wires and flakey relays are a couple
off the top of my head).

With the 960, if it has had an episode of overheating,
or if the radiator transmission cooler has ever failed, the
car can be put back on the road and it may work for weeks
or months or even years, but it will also likely require
further 3k-6k repairs to fix these parts again since they
can't really be fixed correctly.

Basically they are great cars until they break, then
they're probably a write-off because they are so hard to
fix correctly. Make sure the one you're getting hasn't
ever broken.
chris