I went through this exact process a few months ago and ended up with a D3x. I'm VERY happy with its resolution, dynamic range and tonal range (which are big jumps over other DSLRs I've used - my subjective results from looking at prints match the DxOmark tests pretty well). I wasn't able to get test shots of the same subject from the D3x and the H3DII/31, but I looked at big prints from the Hasselblad, and am now making big prints from the D3x that stand up darned well. From what I've seen, the D3x (especially if treated like a MF camera - tripod, low ISO, etc...) puts a big dent in the rationale for lower-end MF. It doesn't dent the rationale for the H3DII/50 and above at all (those cameras will still have much more detail, due to the huge jump in resolution), but you need to decide whether you need all that resolution? I can print 24x36 inches from the D3x, and have it look awfully good, even from 8 inches away. If you own (or will buy) a 44 inch printer, and intend to regularly make prints over 24x36, consider the H3DII/50 or 60 strongly (compare them with the D3x at your largest print size). Otherwise, the D3x has a lot of advantages, ranging from being less than half the price to its AF, handling and ruggedness.
-Dan