There are two new reviews of the SD850 from Canon.
PhotoBlog - positive review, with some good sample pix. They note that the biggest problem they saw was relatively high noise at ISO 400. The review has no discussion of edge blurriness or other lens distortion.
Steve's Digicams - positive review, but very short on details that can't be found in the press release. Steve claims minimal lens distortion and edge blurriness, but has no test pictures to back up his statement. Indeed, this real world shot from his review does show corner blurriness, though it's not an ideal shot to test for this.