It is useful that the Xfinity Stream app exists on my iPhone. However, it is insufficient - it can't display at least some shows on an external device, such as by big screen TV.
This came up because Comcast had an outage in our neighborhood on Tuesday for about 10 hours. (Apparently, for some customers it was 2 or 3 days.) Our Tivo could not record the many shows we like that happen to telecast on Tuesday night. Xfinity Stream does enable us to access those shows.
However, my device is an iPhone 8 with its relatively small screen. Due to licensing restrictions, Xfinity Stream refuses to allow at least some shows to display on an external device. The alert message mentions that AirPlay is not allowed; it also refused to display through my Lightning-to-HDMI connector to my TV.
So, I would be pleased if Comcast would arrange better licensing with networks - in this case, CBS - to allow customers to display to an external device. Or to restore the Video on Demand function via the cable connection.