You'd think their findings would be pretty boring—"hey, it's a Wii, but smaller"—but what they found with regards to internet connectivity is interesting.
Unlike the Wii, the Wii Mini doesn't ship with wi-fi, this we knew. But what DF found was that even a Wii USB ethernet adapter failed to get the console online, meaning Nintendo "deliberately nerfed any kind of internet access". They even went to the trouble of removing sections of the Wii's menu so you couldn't configure online access. Bizarre.
Even weirder is that the console doesn't support component cables. A standard in home entertainment for a decade (you could even get component cables for the GameCube), and even in this HDMI era still a means many people use to connect their console, the Wii Mini only supports composite cables. You know, the red, white and yellow cables your SNES used.
Technical compromises aside, they also put one next to a regular Wii to find... it's not even really that "mini".
So it won't play GameCube games, won't go online and won't use 21st century AV connections. Most pointless console "upgrade" of all time? Surely.
Nintendo Wii Mini review [Digital Foundry]