In October, the Cemu emulator — which allows Wii U games to be played on a PC — could barely boot Mario Kart 8's menu. Now, just two months later, it's doing an OK job of actually running the game. The video below shows how quickly progress is being made on the emulator. On the right is what Mario Kart 8 looked like on version 1.1.1 of Cemu. On the left, the latest version, 1.1.2b, running on an i7-4790K with a GTX 980.
There's still a long way to go on development of Cemu. MK8 here is still missing a lot of effects (here's another video on a slower PC), and as is the case with most emulators, a lot of other games are still struggling to be even remotely playable:
But hey, this is a long game. The Dolphin emulator (for GameCube and Wii games) is still being worked on, honed and perfected, and it's been around for years. Progress on emulators tends not be measured in massive milestone moments (at least, not beyond big early gains like this), but in incremental improvements, the kind that make you look back a few years down the line and realise, hey, these games are running pretty damn well.
To get an idea of how progress on Cemu is shaping up, here's the emulator's changelog.