I've received lots of emails and have had more communication with Canon about the problem with Digital Photo Professional generating soft images from Canon EOS 5D Mark III RAW files.
There are currently two workarounds to this problem.
The first workaround involves changing the DPP "Viewing and saving RAW images" preference (in the "General settings" tab of the "Preferences" menu selection) from "High quality (recommended)" to "High speed". In High Speed mode, the noise reduction palette cannot be used and moiré correction is not performed, but 5D III images are rendered sharp. DPP's Quick Viewer (which displays 5D III images properly) displays images at high speed, so that this solution works is not surprising.
The second solution is to use a third party RAW converter - namely Adobe Camera Raw 6.7 RC. You can use ACR 6.7 RC to output DNG files for use in Lightroom 4 - which will not support the 5D III natively until a point release.
I do not plan to update the color block noise comparison on the Canon EOS 5D Mark III Review page until Canon corrects the problem because I can see a difference between High Speed and High Quality in my 5D II images. You can too - look for the false color in the "5D II Quick View" example that is not present in the "5D II Edit Window" example currently on the 5D III review page.
My case with Canon remains open and has been escalated. I'll let you know when I learn anything new about the 5D III DPP softness problem. Thanks to everyone that contributed to this post.