Tested. Looks pretty spiffy, though as I feared, it doesn't fill up the screen the way 4:3 HD did. Now, there's a big gap of black at the bottom, even when I set my TV from Native (no overscan) to Natural (slightly zoomed). The games are scaled slightly smaller than the Wii U VC titles, resulting in the gap being on the GamePad as well.
Ah well, it ain't perfect, but it's still awesome. At least Wii VC games can finally be output in their proper ratio.