I’ve been getting some excellent feedback from this thread, thanks everyone!
Also, I have no idea how I missed it when I bought the car, but this is only front-wheel-drive, not all-wheel-drive. I guess I assumed all XC90s were AWD? Oh well, not a big deal. Maybe I’ll get slightly better MPG as a result.
All good news for you if you don't need the rear wheels turning. Less weight, less fuel, less to maintain. No bevel gear or center support bearing or any of the things that fail in the AWD system on Volvos. (Admittedly I don't know much about the newer models like this but certainly the first few years of AWD that I have experienced were not known for long lasting reliability)
A relative a few years ago had a somewhat similar unexpected discovery experience but in a much worse way. He works as a videographer in remote locations and has for years been haling his filming equipment around in a series of AWD Chevy Astro vans that he buys, drives into the ground for a few years, then replaces with the next van. Seems they are perfect size and capability for the stuff he hauls and the places he needs to get to, and cheap to own, without using quite as much fuel as a Suburban.
When he wore out the most recent previous Astro and started looking for a replacement (which are getting harder to find in good shape many years after end of production now) he eventually found a really nice one in Seattle. Apparently the test for determining if there are any issues with the AWD viscous center differential is to make a tight turn with the wheel hard over to one side and make sure there is no driveline bind. He went and checked out this van, all looked good, clean, drove great, and passed the AWD driveline bind test beautifully. Butter smooth. He bought it and drove it home.
A few months later he is out on a filming site and gets into some mud or wet grass or something. Van gets stuck bad. Spinning the rear wheels with no drive to the fronts at all. He gets underneath...... And there is no front driveshaft, no front axle shafts, no front diff.... No transfer case! It's a RWD model. The guy selling it had represented it as an AWD and had even glued the correct factory AWD badges in the right places on the front doors. My relative had never bothered to look underneath. His fault. The reason it was so smooth on the tight turn test was of course because there was no center diff to bind up.
It was a bad deal for him because there was deceit involved plus the AWD feature was the reason he had bought that van, he needed it. Plus resale on the RWD models is less than half what a good AWD brings so when he was forced to (honestly) unload it on the market and start over again, he lost money. Lesson on being smart and careful when you buy. Anyway, at least in your case the situation is different.
COLD AC! 
3 ROWS with LEATHER! POWER WINDOWS AND LOCKS! LOTS OF STORAGE SPACE!
