I'm a pretty big Volvo fan. I've owned three of them. A 240 wagon the ex-wife sold with 186,000 miles. A 240 sedan that I sold with 163,000 miles on it. A 760 turbo (current car) that has 298,000+ miles on it. I also drive a Volvo at work (though it's a semi).
When sold, both the 240s were running as good as ever. I have lost a total of 4 quarts of oil in the 760 with nearly 300,000 miles. That's when a front seal went and it started leaking. The engine still blows no smoke, and with the seal fixed it burns no oil. It starts first try, every time.
As for problems, the 760 trannys from 86 and earlier sucked. 87 and later last forever.
Volvo electrics on the whole are not the best. I don't know about the 70 series, but in both my 240s and the 760 exposed wires and other shorts existed. Annoying, but that's all. The components themselves are great, but they wiring is poor. Usually it takes about 10+ years to start having wiring problems. Normally the insulation just gets brittle and old.
As for safety, most European cars are safe, and Volvos are tops in safety. Even my semi-tractor at work has ABS and an aribag. My 240s (a 81 and a 84) met side impact standards when the fed started requiring them of new cars in the late 90's.
They actually don't hold their value as well as they should, which is great if you're buying one. MBenz will remain expensive forever, but the Volvo's value drops quickly. They retain value better than most American products, but not as well as most European products. It's great if you buy used. A couple years old, and they are very affordable without being worn out at all.
I'll continue to drive mine until it dies. I think I'll be driving it a while longer. I'll hit 300,000 before my next oil change (every 3000 is what I do). I was going to sell it then, but I'm just going to keep it and see just how long it lasts. It's not a brand new car by any means. But if it blows-up tomorrow, I'll still have gotten my money's worth out of it and then some.
Ross