I hope someone will do a Youtube comparison review of using the Apple TV and a Roku with the Spectrum TV app. A lot of the complaints I'm hearing concerning the ATV running the Spectrum app or not issues with my Roku Express running it, but the Roku version of the app has been around for many months and has likely been improved. With my Roku Express, the picture quality is as good as using the cable box, so less good than streaming Hulu or Amazon Prime Video which use true 1920x1080 compared to 720p upsized like most cable companies. With my Roku the channel lag is virtually non-existent as channels are change fast than with the cable box. The Roku remote is certainly a lot better than my older ATV gen 3's remote. It takes a few moments to load the app and to load a channel, but nothing I wouldn't expect from a streaming service. I will say though that like any streaming service, there is a time delay between what is broadcast over the air and even on cable, so if you are watching a live sporting event keep in mind that the streaming is likely 30-60 seconds behind OTA.
Someone asked if it was worth getting ATVs to replace their cable DVRs. First, no recording on the ATVs or Rokus. Second, the ATV costs $180, so you would take 18 months to recoop your investment, but after that it is saving you $10+ per month. If you accept Spectrum's offer to buy one at $7.5/mo, then you will save about $2.50/month for the duration of the loan, then you would save $10+/month. I doubt Spectrum would finance more than one ATV per account though. Personaly, I would go with Roku Expresses at about $30 per unit for multiple cable box replacement. But again, currently there is no way to record on the ATV or Roku so no DVR service unles you keep one cable box.
As a cable box replacement for a second or third TV, I would say the Roku Express is a very good deal and if you are into the ATV then it likely would be too, but more costly.