Stopped down even very slightly, the Canon 50/0.95 is very, very sharp; when I did a semi-organized test of all my Canon 50s a few years ago, it was actually sharper at f/5.6 than the 50/1.2 or 50/1.4. Not that you can tell much about sharpness in a downsampled online pic, but this
gallery image was taken with a 50/0.95 at about f/1.2.
At full aperture, it does have low contrast and very limited DOF, as well as producing weird-shaped flares of light sources within the picture, like this:
As Brian says, though, some of us like these effects!
Side note: Did anybody else notice the listing on eBay the other day for a 50/0.95 in South America? One of the pictures appeared to show it mounted on a Leica M3, so I emailed the seller to ask him what he was trying to pull. He said that the lens does mount only on the Canon external bayonet, but that he had used a "prototype adapter" to mount it on the M3.
Naturally, I emailed him back to ask for more details about this adapter, and if it might ever graduate to being a production item! Will update the group if I hear back...