I own a Nikon D800E, as well as a few Canon bodies and lenses. A 50mp sensor interests me, especialy when I also already have a number of lenses that fit the body of the new sensor.
However, when I compare these Imaging-Resource results from the 5DSR with the Nikon D810, at ISO 100 and ISO 6400, at 200% on my monitor, after upsampling the D810 shot to the same file size as the 5DSR shot, I see no significant difference in either noise or resolution that would persuade me to buy the 5DSR.
On the other hand, those who don't have any Nikon cameras and lenses, and who were thinking of switching to Nikon, can take comfort in the fact that this new Canon 5DSR could equal, on average, the performance of the best that Nikon can offer, with the possible exception of image quality in the deepest shadows, which might not be an issue for most photographers.