I take it you're not in the US where most are still under the 4/50 warranty, longer emissions warranty in some states (like 2)?
It's been a problem and was so much of one that Volvo went with a different manufacturer and design for '02 cars. All the '99-'01 cars will likely need them replaced at least once during their lifetimes, more if the owners keep them longer. They're only about $600 here plus software and labor but not exactly in-expensive for sure.
Me, I'll that the good ol' throttle cable type that never fails anyday but that means older Volvo (if a Volvo) and obviously not as effecient tracs but I don't need that either.