It sounds as if your shooting is similar to mine. I don't do large stuff, crop tiny sections from an image, and worry too much about resolution. Those things crop up from time to time, but less than 1% of the time for me. I'm coming from a D3 and I use high ISO a lot.
If I were restricted to D4 or D800 I'd probably go for the D4. However, I see the D4 as a marginal improvement over the D3 or D3S (I don't do video). So in my case, I'll wait to see what the D5 has to offer.