Nikon D3 seems an ideal camera, too bad the price increased or I probably would have gotten one by now. Well maybe there will be a D4 adding 1080p video. altho hopefully no more mp. I fear that if pentax ever release an FF camera they will just use the extra sensor space to cram more megapixels thus killing one of the big advantages of FF.
Adding more pixels doesn't neceserily mean any negative impact on image quality. In fact, in most cases new camera with more pixels deliver better image quality for a given print size or display size.
Nikon hands down. That's if I had all the money. They've got the best zooms, their latest ones are jawdroppingly good (beats a lot of good primes), but at very high prices. And I love the user interface and ergonomics too.
Given unlimited funds, Nikon would be great.
Limited funds, that's a hard one. A Nikon that has all the features I wouldn't want to go without (as on my K20D/K10D) would be well out of my price range. That's without the lenses.
Don't know what I would do if there was no Pentax...
Probably Nikon (conservative choice) as I like the system, the ability to use old glass (on the more advanced models, at least) and ergonomy/user inferface.
A more radical choice (if I were to wait a couple of months) would be the Samsung NX system, as well as the micro-4/3-system.
I would answer Nikon except: I'd want a platform for a multitude of manual focus lenses, and Nikon doesn't do that well. Otherwise, digital photography wise, Nikon's got good things going.
Therefore I pick Olympus and Canon. I'm not sure I could get over the Oly tiny viewfinder and crop factor, but both makes have tons of adapters available for all sorts of vintage glass.
Probably Nikon, although I used to lust for a Canon TLB when I first got into photography. Nikon's color rendition has always seemed closer to Pentax's and that would be the deciding factor for me.
I kind of went through this when I shopped for my first DSLR a couple of years ago. I have owned Nikon film cameras and still have a couple of lenses. The price difference is huge as I need a weather sealed camera. At the time the D200 bodies were $1500 and the new D300 were 2 grand. I could afford the K10D and even with the 3 lenses I have bought since I am still under that $1500 price. The cheap plastic Nikon D40 and Canon Rebel I had no interest in. They aren't weather proof but they probably float. I would probably still be shooting with film.