The 960 is a great car. I have a '92 965 with 180K miles and it's been the most reliable and least expensive to operate of the three Volvos I've owned (264, 764T, 965). There are quirks and problem areas...as there are with ALL Volvos. Perusing the FAQ is a good idea, it will address most of them, but here are a few:

1) Timing belt- this is an interference engine, which means if the timing belt breaks you end up with a VERY expensive paper weight. Make sure you change it as scheduled. This isn't such an issue on later models b/c the belt was widened to allow for longer change intervals (as opposed to 30K miles like on my '92)

2) PNP switch- tells the electronic transmission what gear you've selected. it sits right next to the exhaust downpipe and gets fried with some regularity. expect to replace every 60-100K miles. failure results in a no-start situation

3) ECC- the vacuum servos tend to fail (one in particular). PITA to replace, but luckily the one that usually fails can be circumvented easily without noticeable difference in ECC operation

4) Sticking Valves- this engine was made for the autobahn...not city traffic. the exhaust valves get carboned up from a lot of low-speed operation and stick, resulting in a "tick" at idle (or in some egregious cases no-start). the cure is to drive more aggressively and use only synthetic oil

5) '95 up have completely different suspension than the previous 960s (which had the 760 suspension) so parts are less accessible (read dealer-only)

Aside from the above, there aren't any other pervasive issues with the 960. It's as close to a 5-series bimmer as any of the rear-drive Volvos ever got. Very nice car.