I haven't seen anyone do it yet. The idea was supposed to be that download codes are the exact same thing as disc from the viewpoint of the retailer, with the same margins. This was supposed to mean that discounting would be exactly in line with the disc versions, but Nintendo has apparently been really slow on rolling this out.
It's not that big of a deal, as $50-60 download titles just means that I'll be a bit more picky with what I pick up on the Wii U. I was only ever going to play exclusives on it anyway as I have a 1080p/60 PC in the same room for multi-platform stuff, so not much really changes. So far with ZombiU, Little Inferno, and Lego City, every penny I have spent on Wii U software has resulted in some extremely high quality gaming without disc swaps. I've just paid a couple bucks more than the rest of you.