Maybe it's just me, but I don't need more than 1080p resolution for watching a video. I don't recall the exact numbers, but I think you need to be within 5 feet of a typical 42" screen to notice an improvement of 4k over 1080p. That's bit close for my taste! Now if you have some kind of enormous video setup that would benefit, then more power to you.
EDIT: I found an article on the subject: http://carltonbale.com/1080p-does-matter/