We got a 145,000 mile '01 S40 for my daughter from a family friend about 4 years ago. It has about 180,000 miles on it now.
It had been well maintained and continues to be a reliable car.

I've heard that '01 is the first year of what is considered "Phase 2" generation and that it had various factory improvements over Phase 1 cars like a five speed automatic (all that's available in US) vs. four speed. Some trim changes etc. too.

The interior is a little claustrophobic for me, but it is pretty comfortable. It's quiet and has good power. It's a little soft in the ride department, but I think that is attributable to shocks that are long overdue for replacement. That's not a fault of the car.

I think like any car, try to find one that has been maintained and hopefully owned by a mature driver. Oil changes, timing belt changes, trans fluid changes etc.

There haven't been any nagging issues with this car since it's been in our possession.
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"Differences of opinions should be tolerated, but not if they're too different" - Sharon Craig

Maintenance records and a check-up by a dealer.

Our last purchase - 2008 XC70 - had records and I was able to talk to the Volvo specialist that serviced it. My dealer found a leaking vacuum pump, a leaking axle seal, and scabby rusted rotors.

The tech that wrote it up was cute - he stated that the pads did not contact the rotors properly.

The dealer that I purchased the car from repaired all the items as part of the deal. New pump, new seal, new front rotors and pads, turned rear rotors lightly and sanded pads - the work looked real nice. (Lincoln dealer)

The only Volvo that I did not have checked out - they looked like a nice young couple - needed work that totaled three times the purchase price!

Of course, I see from your past posts that you do have Volvo experience.