75% of Comcast's footprint doesn't have the X1 OS which means they can't use that app. They will have to use the normal Xfinity TV Go app. Also the X1 app only works while you are at home on your main network as it requires an interface with your box.
And BTW, my almost 3 year old Note 3 does multi window with HBO Go, Hulu and Netflix etc (Xfinity Go app doesn't work for some reason). I can actually run three apps on the same screen at once. So Apple doesn't have any exclusivity on this and multi window is so 2012. Oh I'm sorry, you apple users are only getting to use it now. Enjoy...
That app will only let you watch live tv while your on your home wifi service. The tv go app however gives you the option to watch live channels away from your home as long as you have a good data connection on your device. The live channels vary as well.
I have xfinity but not x1 so no dice. The old coax cable installed by the guy who built my house 20 years ago doesn't support enough bandwidth for x1. Fine with digital cable but x1 requires better coax. No way I am hiring an electrician to totally rewire my house just to get x1. I'd rather buy slingbox. All I really miss that you have is the ability to watch shows you have saved on dvr. I would LOVE to do that. I don't watch live tv. Need to zip through commercials.
I keep forgetting about the Xfinity TV app (I use the TV Go one but I forget with X1 you can use the TV App) so I will need to remember next time something is on so I can watch the channel without restrictions.