I really like my 6S+....like enough that I mess around on it at home, checking reddit and iMore and stuff when I could be using my Macbook or iPad instead. It's pretty good for ebooks too.
Still no substitute for gaming on the iPad's big screen (at least for the games I like to play) or reading comics. The 6S+ is definitely powerful enough to be your only computing device if that is the route you want to go though.