If, if, if
Lloyd Chambers havs an excellent review of the S2 on his DAP site. It's a pay site, in my view worth every penny. Lloyd published a couple of DNG images from the Leica S2 and the Nikon D3X. unfortunately on quite restrictive terms. I have played a bit with those images and came up with a few interesting observations. The key observation is that although the S2 images have without any doubt higher resolution the Nikon images are smoother and have much less artifacts. So I essentially prefer the Nikon images but the look of the images is much dependent on the processing parameters.
I've noticed the other interesting thread on the Lloyd Chambers' review of the Leica S2, but I'm not subscribed to that pay site. I'm not sure I need to see in-depth reviews of equipment I'm never likely to buy. At the moment I feel as though I have enough photographic equipment but not enough time to use it thoroughly and experiment with its potential. Nevertheless your report on your comparison of the DNG images you downloaded is interesting.
As regards equipment purchases, the next logical step for me would be a 5D2. My highest resolution camera is still the 15mp 50D. If I hadn't previously purchased a Nikkor 14-24/2.8, which led to the purchase of a D700, I would probably by now have a 5D2 and one of the new 17 or 24 TSE lenses (or perhaps both).
On my recent river cruise in Europe and Russia, I frequently carried around my neck both the D700 with 14-24, and D50 with 17-55. I must have got asked about 50 times, often by complete strangers, why I was carrying two cameras.
I did my best to explain that I effectively get a high quality F2.8 zoom from 14-88mm and that no such single F2.8 zoom lens of similar quality and range exists anywhere at any price.
When I've got time, I'd like to do a thorough comparison of these two camera and lens combinations, comparing the Nikkor at 24mm with the Canon at 17mm (which is effectively 27mm on FF). My impression so far is that the advantages of the greater DoF of the cropped format, combined with the advantages of the image stabilisation of the Canon EF-S 17-55/2.8, sometimes result in better image quality, or at least not worse image quality.
For example, shooting a fresco in a church where flash and tripod is not allowed, I might use the D700 at ISO 1600 and F2.8 but can use the 50D at ISO 800 or even 400 at F2.8 because of IS, which the Nikkor lens doesn't have. When photographing something more 3-dimensional in low light, when the DoF at F2.8 is too shallow on full frame, I might need to use F5 at ISO 1600 with the D700, as opposed to F2.8 at ISO 200 with the 50D, on the basis that IS provides a 2-stop shutter speed advantage and the smaller format provides a 1.6 stop DoF advantage. In such circumstances, there's no doubt that the 50D at ISO 200 has lower noise and higher DR than the D700 at ISO 1600. On the other hand, there's no doubt that the Nikkor 14-24 at 24mm and F5 is sharper than the Canon 17-55 at 17mm and F2.8.