D800 -- end of medium-format?

The Pentax 645 was not created to push the boundaries of high-iso photography, so it's not a fair comparison. Although I don't own a digital MF camera, all of the images I've seen thus far comparing cameras like the 5D to MF still show an advantage to MF. Don't forget that 36 mp is not double the resolution of 21 mp. I suspect that in certain critical applications, it does still make sense to buy MF. I suppose we will have to wait for direct comparisons to judge for sure.