I'd call a significant loss of detail in the middle of the photo something I regularly notice on my 27" iMac or a retina MacBook Pro. If I didn't care about it, I wouldn't have bought the D800 and the lenses I have.
One place I DO care about it especially is when I have to grab a shot of someone or something FAST and don't have time to zoom or get closer. Having the lens able to resolve a full 24 MP decides whether the crop of that shot is going to be useless or not. While my father took photos of me occasionally as I grew up, he never captured anything like what I have been able to of my children, which I can do every day, in amazing detail, and share immediately with my extended family and close friends far away. Recently while playing at the park, I was able, from about 50 yards away, to capture some amazing moments as my daughter and her friends were playing naturally, completely unaware of the camera. I could even see the detail in my daughter's smile, which made it all the more special.
When I've compared older photos taken on cheaper cameras, the feeling from the photo is that it is of sometime distant and far away. With the D800 and the best lenses available, the sharpness (all else being good) to me seems to bring the experience in closer as if it were right now. Then there's the enjoyment of having taken an awesome photo I, or my family (and friends when I take picture of their family) can enjoy looking at for a long time in the future.