Nintendo made it clear that the Wii U would not upscale or enhance Wii games in any way, yet my TV states that it's receiving a 1080p signal when in Wii mode. I can also enable just scan now to get 1:1 pixel mapping, which can only be done with 720p signals and up on my set. The Wii U definitely isn't outputting Wii games at 480p... Just wanted to pass that along.
I do notice a difference in the picture. It looks a bit more like what a DVD scaled to 1080p in a Blu Ray player looks like; obviously too fuzzy to be HD, but not as soft and weak looking as the Wii at 480p (I could compare them directly during the transfer). Good enough news to make all that SD card swapping worth it.