I tried it on a bee image. The bee was not a person, so it did not work.

I tried a few cartoon images. Realistic styles (most of Avatar: The Last Airbender, most of Ghost in the Shell) work well. Semi-deformed styles (Avatar gag faces, Samurai Jack, The Simpsons) usually didn't work or resulted in artifacting. Non-human cartoons (Spongebob, Adventure Time) never worked.

Some photographs which had low contrast between subject and background were not as cleanly cut out. It was good enough that I wouldbe able to import the mask as a starting point and clean up the edges manually.

Photographs in which faces were obscured where handled surprisingly well!

Would love to see this as a native feature of an image editor.

From their about page: "Our AI is trained to detect persons as foreground and everything else as background. That's why it only works if there is at least one person in the image."

I tried it with a photo of a crowd of people and it chose around 20% of the people spread randomly around the photo and removed the others.