I bought a D800. At first I was in love with specs. i.e. 36 mp. Then after shooting lots of wildlife with it, I felt it had no visual advantage over the D3X I had owned, and sold, to get the D800. I ended up buying a D4 and decided the optical performance and the high burst rate proved a real unexpected winner for me. Anyway, I wanted a lighter second body and optical quality the equal of the D3X and felt after using the D4, that the D600 and 24 mp would provide at least as good, and probably better image quality then the D3X. So I sold the D800 and eagerly await my D600 sometime next week. I am very easy on my cameras and love the extra toughness of the D4 but for almost all my needs, the quality of construction the D600 appears to have is more than adequate.
I don't make large prints, but do enjoy my iMac 27'' with intel i7 processor, which is what I use almost exclusively for viewing, So the real optical advantage of 36 mp seldom proved of use to me.
I read an article that soon DX level cameras will be moribund. I agree. Today MOST users are content with iPhone quality pix which is just right for Facebook and the "social networks". So the big boys like Canon and Nikon may end up in big trouble if this comes to pass. Obviously almost anybody reading this website is not the "average" user. Nevertheless, Nikon and Canon may lose a huge market as point and shoots and DX level cameras may become like 8 track audio cassettes. I am glad I switched to cameras with FX sensors. There will always be a pro/advanced amateur market, but if I were Nikon I'd be thinking hard of how better to compete if DX goes bye-bye.