They work fine for me.
Not always perfect, but good enough.
Mine are pretty far removed from the router, especially the one in the back yard. At times the Live view can take a while to start working.
I have two of the Circle cameras (bought from Amazon), and the Circle doorbell (bought from Logitech, don’t recall why).
When a person is detected by the doorbell, it pops a window up on the Apple TV, which is nice.
When a known person rings the doorbell, all the homepods announce who it is. lol
You can have recordings made for different types of motion - people, animals, vehicles. You can also screen out areas, so I have the street and neighbors driveway masked so a recording isn’t triggered by activity there.
It will also let you know when a package appears (or some clever shadows).
I use mine exclusively through HomeKit, got tired of paying the subscription for the other brand I had, and they were kind of crap.