Like I mentioned, I have the Spectrum app on my Apple TV 4K and not for anything but sadly, the Spectrum app sucks. The guide is half crippled and doesn't let you view program info without switching to the channel, it doesn't tell you whether an episode of a show is new or a re-run, and the biggest problem is that it's only capable of 2-channel stereo audio. It won't pass Dolby 5.1 so any movies or shows that have a full 5.1 or surround soundtrack will only come out in 2-channel stereo.
I ended up getting a regular Spectrum cable box which does do full 5.1 audio, although the video is limited to 1080p.
That said, the only reason I bought the Apple TV is for the Spectrum app. Because Roku and Spectrum are having their little childish spat, it cost me $180 to find out that the Spectrum app is almost useless. Fortunately the Apple TV 4K is a really good device so I've been using it as my primary streaming device instead of the apps on my Roku TV or my Firestick 4K. The Firestick 4K is almost as good as the Apple TV though especially with the ability to sideload apps.