I got this doorbell a while back and had time over the christmas break to install it. For the record, my existing doorbell is this one, Honeywell RCW110KB1008/N
which has a 16V/10A AC transformer (sorry can't comment on the question on DC transformer)
Installation went very quick, however the doorbell was ringing on and off as I had forgotten to add the chime that was included; once I added it, no issues whatsoever.
I can say that I'm very pleased, app is very quick to both let me know when there is human detection as well as when someone rings it prompts on my phone to use the speaker, etc.
I'm using this in BI and it's working great, I've had it on non stop for 2 weeks, no trouble, and the weather has dipped to -25 Celsius a few times in the last few days - no problems.
The only complaints for me are:
1) the LOREX watermark at the top left cannot be removed from the stream.
2) if I listen to the audio and there is nothing going on outside, there is always some weird clipping sound (think of a popsicle stick in the spokes - not the same, but similar to that); not sure what causes that, however if there is speech, cars going by it picks that up and you don't hear the clipping sound.