(cont'd)
Eventually, in the candid/portraits/details category... two shots from last week, a stranger in a crowd.
Quite harsh zenithal sun, shot handheld @ f5.6.
No processing except one-click Adobe profile RAW conversion to JPEG in ACR.
Final image crop inside full original 24MP frame (dimmed areas):
100% crops:
(note details on skin / fingers + smooth natural transitions)
Next shot, subject slightly in motion:
100% crops:
(note fine skin lines, watch in the shadows)
(OOF area)
(belt & label, extreme bottom edge)
(belt & label, extreme bottom edge) @ 200% crop:
Please again bear in mind that all this is 8 bit jpeg direct processing from RAW, crops and enlargements from jpeg.
(+ forum automatic sharpening? Certainly look less "natural" and precise once posted...)
Anyway, all look much better in PS here, and even better as TIF or in print.
Other notes / Conclusion:
There seems to be a tad less noise on the SD1 samples than on my D3X shots (or 5D or D700), but 1/ it's quite probable (and visible) that NR was applied on most of the Sigma the samples 2/ IMHO noise is very convincing on the D3X and is the most analog-like noise seen on a FF DSLR. 800ISO portraits look perfect on print.
There's significant amount of CA showing on the SD1 samples (quite nasty if you ask me) which is basically absent from the D3X.
Maybe related to processing, but still a matter of concern.
We have no clue about exposure and WB corrections applied on the SD1 samples. One of the great strengths of the D3X is an incredible AWB (most of my shots' WB are straight from camera - all shots posted in this thread are uncorrected AWB) and an excellent exposure metering.
Some of the SD1 samples published till now seem to have undergone serious to severe oversharpening -in order to impress as far as detail is concerned? Personally, i find most of these details somehow artificial and unconvincing.
That said, and also thinking of the first two samples available last year, it looks like it's a good tool for portraits in studio controlled conditions. Not unlike the 5D MkII In this regard, and maybe a step higher in terms of enlargement capability.
Otherwise and for now, color rendition, micro contrast and DR are questionnable all the same. A SD1 body in hands will be needed to get a more comprehensive vew.
Reliability wise, operating a D3X is super smotth, mine quite simply never missed a single shot. I sure did on occasions, but not the body.
Re the SD1, only time will tell.
Finally, let me stress out that AFAIC uprezzed resolution details is just part of the equation in modern photography, and for most needs a relatively marginal criteria in systems choice.
Using best practice routine (tripod etc.), D700 shots are regularly printed on 1m+ (40"+) long size posters with great professional results. Lately we printed D3X crops on a 4*3m (approx. 13*10 ft.) banner, and it was from a 15MP file after cropping the original shot. Meaning a 5 cm (2") long with 13 millimeter (1/20th inch) diameter piece of equipment is blown up to more than 2 meter (7 ft.) long. Needless to say, these are not designed to be scrutinized at pixel level, but in a reasonnably large office or even a standard 800 sp. ft. showroom, it looks pretty good. And i mean by that: "happy client".
Of course, for such specific tasks MultiShot MF backs are ideal (though today i wouldn't trade the true versatility and ease of the top DSLR, if not for owning both systems -but that's me and for another discussion).
Just saying, nowadays resolution is not always a major issue for the mere mortal photogs among us who cannot justify investing in a 50K$++ dedicated kit.
That's it for my 0.02...
(had to type all this pretty fast, and posting a large number of images is not exactly ergonomic... sorry for the typos etc...) 
