Just started a subscription to DirectTV Now (as a bundle with my AT&T mobile plan). For the last week I've been trying to use this service with my Apple TV and it has been a completely miserable experience. The app/service is buggy, unreliable, crashes, quits mid-stream, etc. Also, the app design is similarly poor. In total, definitely the worst streaming experience that I've had after almost 10 years with the Apple TV (and other streaming devices).
It seems that the live channels are better than the on demand content. The latter is very buggy and will sometimes jump back and forth or get caught in an endless loop or just quit during playback.
What makes it worse (for AT&T/DirectTV) is that there are really wonderful streaming apps for the Apple TV. Just check out the PBS app (free) or even Netflix. I suspect that they need to start over from scratch with the DirectTV Now app and service, completely new design and new code and most likely a completely new team (both engineering and management). It's really that bad and since this service was introduced one year ago I can see no good excuse for its continued poor performance.