I've wasted so much time trying to watch with this service and it's hopeless, it freezes and buffers endlessly. I've spent a lot of time with NowTV support working through their fixes and nothing's improved.
I use Netflix, iPlayer, All4, YouTube and Spotify with absolutely no issues. I also play games online with no issues.
The app on my phone plays content fine as does the browser version on my laptop, but these aren't very good options for several people in a room. The issue is purely the PS4 app and until it's sorted this service is pointless so I'll be cancelling if not resolved soon.