It does 4k HDR and ATMOS. What does it lack?
Should have just gone straight to the AppleTV, which is where I ended up. Better UI, not shitted up with ads, less jank and crashing (friggin' Android), and none of the problems I'd see with playback of certain combos of audio and video codecs on the Shield. If not for the weak codec line-up, even sticking with Roku would have been better than the shield (yeah, it's shitted up with ads, too, but not as bad—hell, the Apple TV kinda has some, but again, less bad).
I have the older (not 4k) Shield, I'm just using TV apps since upgrading the TV, since I couldn't settle on anything else. Tried and didn't like the 4k Fire Stick.