The R-D1 uses the same sensor as the Nikon D100. Crop factor of 1.5x, IR leakage not as high as the M8- but is there. I've seen some comparison images that indicated Blue response was low, similar to sensors in the 90s. Kodak introduced new chemistry to their sensors in the late 90s to improve blue response.
I almost picked one up recently, was $750. I had just bought the APO-Lanthar 50/2 coming out, so spent my "camera money".
I also have an M8, which is now the recreational camera. I bought it 10 years ago for $2500 with case and spare battery, had been used 3months. The M8 came out in 2006, but has a CCD designed by Kodak with offset microlens array for optimal use on M-Mount lenses.
To add- I recently got into a discussion regarding reviews of M-Mount lenses on Sony cameras being used to judge performance on Leica digital cameras. The review of the 7artisans 50/1.1 stated there was "Whopping 4.1 F-Stops of Vignetting". The reviewer did not make it clear that this was a function of the sensor not being designed for M-Mount lenses. The Vignetting of this particular lens is 2.5F-Stops on my M Monochrom. Stated differently: the Sony lost 3 times the light at the corners compared with my Leica. The comparison shown in the Linked Article would have been more interesting had the R-D1 been compared with an M10.