I'm actually trying it out as my daily driver for a week or so trying to answer that exact question. I've got Pihole on my network so it won't be a true test of Vivaldi alone, but I can say with the weaker Manifest V3 version of uBlock and whatever Vivaldi has built in, I've been satisfied. Granted, it's just been a day, but I tried my damnedest to get some YouTube ads to appear with no success.