You sure found a good deal on the Hasselblad outfit. Was it on ebay? I would be interested in your impressions of how it compares to the Nikon going forward.
Yes, I bought that H3D-31 on ebay. Nobody else bet, so it went for a really good price, but I don't feel I can give you a really meaningful answer yet: I have only had the camera for a few days, so I have not really tried it yet. Furthermore, the camera is fine but the back IR window has spots of mould. I could clean the outer side (I posted how I did it in another post), but I can't clean the inside without dismounting the glued window, so I will end up sending back to Hasselblad in Göteborg to have the window exchanged. According to their web site, this is a fixed price of €326,- plus tax, which is reasonable. But it means I will not be able to use the back for at least a month. On top of it, I need the back cover to send it without the camera. The cover is ordered, but delivery should take about 10 days… So I'll have to be patient. In the mean time, I can use the back up to f/5.6-f/8 without the spots being too visible. I may also use the camera with film: the H3D is the last digital model which accepts the film backs.
What I can say, however, is that a comparison of the cameras on output only makes little sense. The cameras are very, very different in their use and I will certainly not make the same pictures when I use one or the other. For landscape photography, which is what you seem to be interested about, I would say that the D800 is more adapted if you want to produce the typical over-saturated, wide-angle panoramas which are fashionable at present, while the Hasselblad may be more adapted to a documentary in the style of the New Topographics or to details with little depth of field. The Hasselblad is big and heavy, especially when taking the lenses into account and I would not take it to a mountain.
As to the D800, since I have a bit more experience with that camera, I do not like the rendering of many Nikon lenses or the skin colors the camera produces (which is my motivation to get something else), but the autofocus is miles ahead of the competition (not useful for landscape) and some lenses like the famous 14-24 have no equivalent anywhere else. And of course the D800 can be used with Zeiss lenses, which have a rendering completely different to the Nikons and which I learned to appreciate on my Sony A900.
The real question you should ask yourself is, maybe, what kind of landscape pictures you want to make. What kind of aesthetics are you looking for? How should your pictures look like? What colours? What rendering of sharp or out of focus zones? What landscape will you photograph (in terms of light, colours but also accessibility)? When you know what you want to get, the type of camera should be evident.