Investing in a new Apple TV when I have such blind hatred for the previous iteration is probably incredibly stupid... but I have a huge chunk of movies and music purchased from the Apple ecosystem, so it's kind of a necessity to keep up. Especially now that Apple is offering free upgrades to 4K HDR video for all your previous movie purchases (when available, of course).

And... I suppose I should just run through the fine points rather than re-hash the broad strokes, since those are mostly the same.

Apple TV Box
Looks identical to the previous one. I'm sure there's probably quite a few differences under the hood, but I ain't opening it up to check.

Shitty Fucking Apple Remote
Still unbelievably fucking shitty. The touch-input area is just as stuttery and unresponsive as ever, making simple tasks like navigation frustrating... and complex tasks like keyboard input unbearable. I fucking HATE this piece of shit. The only difference between the new one and the previous one is that the "menu" button has an elevated white circle drawn around it.

Shitty Fucking User Interface
Still unbelievably fucking shitty. If you've purchased anything more than a dozen movies or TV shows, you'll go absolutely bat-shit crazy trying to navigate through pages upon pages upon pages upon pages upon pages of crap. Especially when you're forced to use the unbelievably fucking shitty remote.

4K
The 4K picture is totally great. Remarkably, I've not yet gotten any of the streaming errors or throughput problems which plagued the previous Apple TV. Considering that there's probably a lot more data coming through the pipe for a 4K picture, this is truly shocking. My guess is that there's new compression tech that makes this possible... but only time will tell as to whether or not Apple's unbelievably fucking shitty media delivery will rear its ugly head.

HDR
I have an HDR-capable TV. My stereo receiver is HDR-capable. When I plug Apple TV directly into my TV, the Apple test-program says that HDR will be used. When I plug into my stereo receiver, however, the Apple test-program says that my television isn't HDR capable, and it will downgrade to regular color fidelity. And, of course, since this is Apple we're talking about, there's no way to just force the fucking thing to deliver the HDR signal that my receiver and TV are capable of. This kind of shit drives me i-n-s-a-n-e. Do it Apple's way or no way at all.

Picture Quality
I put in my copy of Kingsman on 4K HDR Blu-Ray then started up Kingsman 4K HDR from Apple TV. Then I switched between them. Not even close. The 4K Blu-Ray picture is superior in every possible way. The color is better. The clarity is better. The contrast is better. Black levels are better. There's literally nothing that's not better on 4K Blu-Ray. The Apple TV 4K image has crisp details in fine items like hair and text... but mooshy areas of softness any time the color values are similar, particularly in bright spots. This is undoubtedly a function of the high compression, but I have no idea what's responsible for the other issues. The bright, almost washed-out haze that permeates every scene is just bad compared to cable or Blu-Ray. I don't recall the older Apple TV having this problem?

Audio
Seems on-par with what I got from the Blu-Ray. Rich, full sound.

HomeKit
Apple's pathetic attempt at Home Automation... which they call "HomeKit"... is pretty awful. I'm guessing a big part of why it's awful has to do with it being run through Apple TV. Sure it beats having to purchase a dedicated hub, but maybe with a dedicated hub it would have been worth a crap. When I swapped out the old Apple TV for the new Apple TV, it took several attempts to get HomeKit commands working... but at least they ended up working without my having to do any crazy setup revision or anything.

And So...
If you're dying for the best possible picture on your 4K HDR television, you'll have to keep buying 4K HDR Blu-Ray discs. Apple isn't even in the same ballpark. That being said, the picture quality is a step up from non-4K non-HDR Apple TV. So... until HDR 4K Blu-Rays drop to the same price as Apple TV digital purchases, you may still gain benefit from the latest and greatest Apple TV. The fact that Apple doesn't charge a premium for the higher quality is a nice bonus for anybody investing in the 4K HDR... but don't be fooled into thinking it'll be the same quality as the equivalent Blu-Ray.