Update:
This thing is great! WiFi connection is rock solid (not seeing any reliability issues at all).
The image is excellent and the nighttime image is very good. (with the app and with
Blue Iris)
The included wedge mounts (left or right angle or upward/down angle) are handy and show excellent attention to detail.
The doorbell adapter works correctly, and the app can configure the adapter to have the push button depress time be set from momentary to up to 5 seconds (I have the adaptor operating a 24 VAC DPDT ice cube relay that activates the legacy electronic ringer as well as a Insteon sensor for my HA system) . This gives cloud free operation and no reliance on the app.
The app is actually very good (using the RCA variant). Button press notification is very quick (almost instant) on iOS and is dead solid reliable, and the intercom function now works quickly and the sound quality at both ends is loud and clear. Configuring the alarm zones, notifications, WiFi, even firmware upgrades work fine. It even has dewarp if you scroll the image.
Configuring the RTSP and editing parameter with IVMS-4200 software is the 2 areas that are a little fiddly. But once set, I have not touched had to them again.
I replaced 1 RCA DB1 with this and now am replacing the other 2 (which are junk).
I am seeing performance on par (or better) than nest or Ring without the deadly subscription fees and being married to the cloud.
FYI don't bother with the building centre 16 VAC home-owner grade transformers. You can get a HVAC 24 VAC high current transformer from a HVAC or electrical wholesaler for less and will eliminate any power issues. (I have a DIN rail mounted one to go along with the ice cube relays to make a professional install)