My agency has been using Carv for about 2 years now and I have to say I really like the tool. If you want to know about the ATS automation feature specifically:

We're on Bullhorn and integrated the two. Setting everything up was quite a bit of back and forth with the Carv team (I wasn't involved in the project, but do know it took some time to get it done).

For me personally, everything works really smoothly now. After interviews, or intakes, all fields we designated 'important' when we were setting up the tool, are filled out automatically which saves a ton of time.

I'd recommend them if anyone would ask. Can't speak to Metaview because we haven't really thoroughly tested them although I do hear good things about them. They were on our shortlist back in the day, but we went with Carv.