I'd guess Rivian SW is good, because Volkswagen's SW got so bad they hired Rivian to rewrite it for them. (That contract is the only thing keeping Rivian afloat right now.)
Rivian software is pretty meh. I've never had a safety critical failure while driving, but have had multiple other issues including being trapped in the car unable to exit until after a reboot. Worse -- rivian has no mechanism for reporting software issues. If you don't want a service appointment (which is available in 3 months!) then don't bother reporting it.