With non-digital SLRs, I never trusted anything coming from Japan

and now it seems like Nikon and Canon invented photography - there are a lot of other companies that make really interesting cameras, too.
And that new organic sensor developed by Fuji and Panasonic might revolutionize everything (29.2 stop dynamic range).
That said

I had a lot of cameras from different brands over the time, and I always purchased them based on whether they were said to produce good image quality. I also never purchased a lot of glass, so I never got really tied to one brand.
I'm not a pro photographer, I don't shoot astro, fps and 8 minute exposure times are irrelevant for me. I had a Canon DSLR before getting the Nikons but was unhappy with some aspects, namely dynamic range and colours in difficult light conditions.
I searched for a solution and a knowledgeable friend pointed me to Nikons new sensors, on the D600 and the D800. I bought the D600 first, had the sensor dirt problem, and bought a D800 consequently (I know, others might have reverted to Canon, or another brand, I didn't).
I'm happy with the D800 because it seems to be the right camera for me. The dynamic range is excellent (as of today, in a few years it may be obsolete). I can shoot exactly the type of pictures I want to shoot, without worrying all the time about whether that bright stretch of sand should be in there or not because if it's in the sensor's dynamic range would be exceeded. Rather, I compose the image I want, and shoot, and the result is technically good (whether the image is good is another question, but that is the responsibility of the photographer, not of the camera).
Furthermore, all the controls I use for my type of shooting are readily available. There's a button or a switch for everything I really need to have readily available, so operation-wise the camera does what I want. Plus, personally I find the use of the camera both in controls and menus intuitive - with the Canon I struggled a bit, with the Nikons I find everything immediately, don't know why.
Then again I have a friend who shoots astro - Canon seems to be much better in that market, and if I look at his pictures, they're just as good as mine. OTOH, none of his images requires a lot of DR - it's just the kind of images he wants to shoot.
I don't really think that 4 or 6 fps make a big difference, but for those who need the additional 2 fps, they probably make a difference. For them, the 5D-III is the better choice.
I like how Nikon tries to capture natural colours. They never seem to try to exaggerate, even though their colours sometimes look a bit plain. Canon colours are sometimes more vivid out of the camera, IMHO. I personally prefer to add that in Lightroom, if I want to add it. But I applaud Nikon for resisting the temptation to make their pictures look more flashy, and give me the option to chose, instead.
As for the glass, actually I also perceive the Canon glass as being a tad better, or at least more interesting options being available. But all I need is an excellent standard zoom, and two or three primes like 35-50-85 for those occasions when utmost quality is desired.
For those who need special lenses, they have to decide for themselves where they find the better options.
So basically, as I see it, it's not Nikon versus Canon, as there are a lot of other interesting options if you want to take great pictures (not to forget the excellent m43 market with the OMD and other great cameras which may fulfill the needs of many good photographers better than bulky DSLRs do). And, which brand or camera is 'better' is based on your needs. You cannot say that one brand is better than the other, you can only say it is better than another for a specific purpose.
I would easily move away from Nikon if they would fall behind in image quality. But right now, I really like those current Nikons, and feel that they are the best choice for me. BTW, the D800 does have an HDR feature (I saw this question at the start of this thread).