The S70's seem to be a pretty reliable car over all. But there are not that many at the moment over 100K miles. The XC70's seem to have a decent record. There was talk of transmission/trans-axle problems with the XC70's over 100K miles. I haven't gotten a good read on whether it was a real problem or a lack of maintenance by the owners. One point the techs have made is don't expect too many of the FWD's to see 200K. They seem to think many will get junked early due to the high cost of routine maintenance needed over the years.
It must be the 10K-15K mile oil changes they are seeing at the dealer with present owners. The XC90's as the techs at the dealer say are TOTAL JUNK.