Interesting that the Pentax K-5 tops the DxOMark ranking for APS-C sensors followed very closely by the also new Nikon D7000.
DxOMark ratings:
(Low-Light ISO) (Dynamic range)
Pentax K-5 1162 ISO; 14.1 Evs
Nikon D7000 1167 ISO; 13.9 Evs
Pentax K-x 811 ISO; 12.5 Evs
Pentax K-r 755 ISO; 12.4 Evs
It would appear that the Pentax K-5 and Nikon D7000 are pretty close;
the K-r and K-x are also close to each other.
A few points might be measurable - but they are unlikely to make much practical difference in real-world photography - however the K-5 and Nikon D7000 both seem to have significant improvement according to the DxO figures over the K-r and K-x.
It's a pity that Imaging-Resource have not published their standardized test images for the K-5 (or K-r) so we can see some results that we can compare directly with known cameras - however they have recently put up the test samples for the Nikon D7000.
I know this is not comprehensive - but I just wanted to see if the images had any significant improvement at higher ISO JPG, as that is what interests me using the Nikon D7000 as a sort of "substitute" for the K-5 compared to the existing K-x which had outstanding High ISO performance for its time to see if the K-5 is likely to have noticeable improvement at high ISO over the K-x (hope that makes some sense) -
ISO 6400
ISO12800
It seems to me that visually there is no major significant improvement for High ISO images of the Nikon D7000 (K-5 likely to be similar?) over the existing K-x - other than more pixels. But please remeber this is a very limited view using JPGs - one could download the RAW versions and process them and do a similar comparison - but this quick and dirty comparison shows me for the time being at least that this new generation of dSLRs (K-5 and Nikon D7000) are improvement for 16+Mp but not a significant visual improvement at Higher ISO than the K-x (and probably the K-r) despite the significant improvement in the DxO figures