Bryan has posted ISO 12233 crops for the new EF 35mm f/2 IS. In his News post, he states:

The Canon EF 35mm f/2 IS USM Lens results are remarkably better than the results from the replaced Canon EF 35mm f/2 Lens in the mid and peripheral (corner) areas of the image circle. Results in the center appear slightly better in the IS lens, but the differences are very slight - not surprising as the old lens was very sharp in the center...Here is a Canon 35 IS vs. 35 non-IS comparison (use the mouseover feature to see the differences).
Also of interest to me is the Canon 35 IS vs. 35/1.4L comparison - wide open (which, granted, is a stop wider for the L lens), the 35 IS appears to produce a sharper image all across the frame, with less CA as well. Even with the 35L stopped down to f/2, the new non-L is a fair match for sharpness across the frame, and the L lens still has more CA.

I hope this spurs Canon to come out with a 35L II sooner rather than later...