That's exactly what I was talking about, if you had 720p native content on a 720p native display next to an otherwise identical 1080p native display showing native 1080p content, at some point of distance, your eye would no longer be able to perceive a resolution difference (screen size dependent, of course).
So, in my opinion, if the eye cannot distinguish between native 720p and 1080p on a display the size of mine, at the distance of my seating position, I see no reason to lose sleep over whether or not I'm getting 1080p.
Absolutely, there are visible differences between native 1080i and 1080p, but the only time you should see a difference between a 1080i or 1080p transmission of a 1080p native source is if the display video processing is inferior.