Confirming this. Got a pair of these for myself and my roommate, here's our experience so far for any future buyers:
First off, the build quality is excellent. They feel slightly heavier than the traditional SNES controller and slightly thicker (because these have an internal chargeable battery), but they are incredibly comfortable and responsive. The d-pad, start/select, ABXY, and shoulder buttons all feel crisp and familiar.
Second, these work best as a standard bluetooth device. Turning it on in bluetooth mode, it was instantly picked up by our Steam Link and was very responsive. We were also able to easily pair them both with a smartphone and use them as controllers for some mobile games. My roommate has an NES emulator on his phone that it worked smoothly with.
Third, after upgrading the firmware from the 8Bitdo website (pretty simple on Mac or PC), we were able to get them to work with both the WiiU and the Wii. This requires a lot of patience, however, and I'm still not really sure what we did to get them to work when they did. After several attempts hitting sync between the two devices, they eventually just found each other; WiiU took less attempts than Wii. Playing Super Mario RPG on Virtual Console on WiiU was perfect once we got them paired, though! Using them with the Wii required syncing a WiiMote first, then the controller, then swapping Player 1 and Player 2 from the Wii's controller menu, then going into Homebrew Channel to play. Definitely a hassle, but doable.