Would definitely be interested to hear other users' experiences of the new ATV with a 1080p TV.
I am interested as well. No current Apple TV or 4K sets. I would be buying the 4K model for the faster processor, gigabit networking and general future proofing as much as possible.
Thanks! this what I was hoping to find in this thread - a few real tests of this.
I find "HD" quality varies, I wish I could watch real HD and I think 1080p is sufficient for me, especially with slightly less then perfect vision and sitting about 10 ft away. But much of the program out there is low bit-rate HD so any action and the quality falls apart to SD. My hope was I could get the new 4KATV, stream the 4K content with 4K bit-rate and downscale to 1080p - resulting in noticeably improved HD quality overall.
Any more real-world examples out there of 4K ATV on 1080P TV?
I got my ATV 4K yesterday. I also have the ATV 3 and it is still connected up to my receiver, so easy to make a Comparison. Just to say that I really like the quickness of the 4K, & i do like the new interface, & the remote versus the old version.
Here is my set up - nothing special but it fits together quality-wise

TV is an LG 50" Plasma THX Certified 1080P
Receiver is an Onkyo TX-SR608 Feeding a Canton 5.1 surround system
400Mbps Downstream Internet distributed via an Asus RT-AC87U Router
Ok, on to the comparison. Up to now I have watched Wonder Woman & an Episode of The Expanse on both units. Picture Quality Wise I detect no real difference, & that is not really surprising seeing as the Receiver sits in between. The streaming itself feels more solid (No sensation that not enough of the Movie is buffered), & the starts of Movies or TV episodes are much quicker. Sound Wise it seems a little more defined, although that could be me just wanting it to be so
You now have some changes with the audio output set up:-
On the ATV 3 I had Dolby Digital & Audio Output set to Auto, & automatically got the Dolby Digital Logo lighting up on the receiver (See more below)
Now with the 4K you get "Audio Output" "Audio Mode" & "Surround Sound"
Audio Output now relates to where the 4K sends the sound; I had the choice of the 4K, the ATV3, or any of my Wi-Fi connected speakers in other parts of the House
Audio Mode is the new name for what was called "Audio Output" on the ATV 3 - choice of Auto or fixed to 16 bit
Under Surround Sound you have
Best Quality Available
Dolby Digital 5.1
Stereo
At first I had it set to "Best Quality Available", but then noticed that I did not get the red Dolby Digital indicator either on the Film or the TV episode, although the sound was the same as if I set it to DD 5.1. On further reading, it turns out that on "certain" (read "older") receivers, the BQA setting will not activate the indicator even though you are actually getting DD 5.1 or 7.1 depending on your set up.
https://support.apple.com/en-us/HT204069
So overall I am very happy. Definitely a good step up from the ATV 3 in many respects, & I'm all set for when I get a 4K OLED later this year along with a new Receiver.
If I can help in any way with any questions, happy to!