I started back in 2016 with DirecTV Now, which turned into AT&T TV Now, which has now turned into AT&T TV. Thus, I'm a long-time customer, through the ups and downs of the young and growing service.
I stream it via multiple Apple TVs and my phone. The interface really hasn't changed on either device since the very beginning, nor have many of the features. I will add that I have not used any other streaming service, so I really don't have much to compare it to. Had I not been able to keep my grandfathered plan and rate from the DirecTV Now days, I'd look to alternatives, but the grandfathered plan is too good to let expire.
I've been pleased with it, for the most part. The Cloud DVR largely sucks, but has improved over the years. It will record things, as you'd expect, but sometimes has glitches with fast forwarding that causes it to go back to the beginning of the recording. Pausing live TV also has been hit or miss. It will pause live TV, but rewinding doesn't always seem to work, and I've never really been able to figure out why. The channel interface can also be glitchy at times, but nothing that really impedes anything, you just sometimes have to exit the guide and reopen it.
Honestly, other than that, I really have no complaints. The free on-demand shows and movies are nice, you can add HBO/Showtime/etc to your subscription, you can use the subscription on pretty much any third party app, etc. I can't comment on the current price/channel selection, because, as mentioned before, I'm on a grandfathered plan that is alot better than what they currently offer.
I'll also add that AT&T TV only allows for two simultaneous streams, but you can add a third for $5/month. Whether that's a dealbreaker depends on your circumstances, but something to keep in mind, as that limit seems to be lower than alot of competitors.