I think the main advantage of this is that spammers remove a number that has Google Screen replying. When I got a first phone with this feature the number of calls dropped from several a day to a couple a week.

The ability to filter per se is quite bad. The calls it decides to screen itself pass through 100% i.e. it listens to an extended warranty call or 5 star hotel call and then rings through as if it's a legitimate call. It's worth noting that only a small fraction of calls go to screen automatically, most just ring and I have to press screen button myself.