Compared to other cars they are similar, but compared to an older 200, 700, 850, 900, S/V90 or possibly a pre 2001 S/V70 they take more maintainance and they do not hold up as well as the older Volvos. The XC90 with the T6 or V8 engine have a transmission that is prone to torque steer and from what I heard it doesnt last as well as the RWD transmissions did.
Aaron Z
I drive an S70, traded it last year because the 850 (i bought it at night, didnt see it was poorly maintained) had lots of small issues, trading was cheaper than repairing as i got a great price for it, and got the S70 with 100.000km less in return) I have looked at an S60 but i simply dont like them. They are much smaller on the inside, about as much leg room as in the 440 models i had. The 440 weighed 1033kg and the S60 weighs 1500kg. An S80 would have comparable room like my S70 but it weighs even more.
The 2.0 diesels, built by Peugeot/Citroen/Ford, are rubbish too, the D5 lasts about double the time and has a Common Rail pump that lasts. Not sure what my next car will be, perhaps it will be a Skoda Superb (Volkswagen technology in a Czech built car, for a decent price, better quality but not so much status- So good prices for used Skodas
)
About runaway cars, when i short circuited my 440 due to a poorly installed alternator wire, i drove an old Ford Sierra 1.8 TD for a month. The turbo seals were gone, and when the engine was hot and you'd rev it, it would runaway because it was fueled by engine oil that the turbo let into the intake. It was quite an adventure, blue smoke like a tractor puller, traffic putting on their fog lights and honking their horns.... It didnt scare me at all, just hit the brakes and kill the engine. After 2 minutes of cooling down, i could drive off again.
When the 440 was up and running again (i didnt investigate the wiring loom at first, but it was only a matter of some isolation tape to fix it) we raced that Sierra to death: It ran only 5 minutes on oil before the engine gave up...
If i had time, i would have an older 240 D6 (with the infamous Volkswagen inline 6 IDI engine) and swap that with a chipped D5 with a stock M90 transmission behind it (bolts right up)