A lot of people are worried about the abysmal number of apps for Android TV and they're right. But at the same time i want to remember everyone that Kodi exists and work beautifully on the Shield. So if you have no problem troubleshooting a little bit to make things work you can use hundreds of addons instead of apps. I have had some problems lately with the Nba app and discovered an Nba addon which works better than the app. I've seen 2 or 3 Amazon Video addons too. Obviously they're user-developed so functionality is not guaranteed, but the number of broken or abandoned addons is very little and repositories are kept tightly clean. Lastly the kodi community is very active and if you have problems you can look up the wiki or write on the forum.
I really don't like having essentially a second OS running atop the primary one and attempting to duplicate most of its functionality. 90% of my needs are satisfied by native Android TV apps and the nature of kodi makes it somewhat annoying to use for only the remaining 10%.