It's hard to know what Nintendo makes of Cemu, a Wii U emulator that's been making rapid progress. Often these fan-based projects take years to come together, but in this case there have been frequent updates, perhaps helped by the similarity - in some respects - of the current-gen system to the Wii.
In any case, progress has been startlingly quick from a technological perspective. Though the emulator is still a long way from being a legitimate threat to Nintendo's system, it's still surprising how a matter of months have seen builds move from returning frozen screens to functional gameplay.
Version 1.4.0, released this week, perhaps claims Super Mario 3D World as its biggest landmark improvement. As you can see in the video below it's running surprisingly smoothly - some are claiming to be averaging around 50fps on their PCs - albeit with faulty lighting and a likelihood to crash.
Below is Captain Toad: Treasure Tracker.
Progress with Xenoblade Chronicles X is slower, no doubt due to Monolith Soft's huge RPG being a particularly demanding game.
Chatter around the recent build points to Super Mario Maker (offline-only) running very well, though titles like Pikmin 3 are still rather slow. Naturally there are also issues, in general terms, with crashing, poor lighting and other quirks.
For the emulation community there's certainly interest in how quickly the project is progressing - it's a closed development group, and in the past it's been made clear that it's staying that way to retain focus and to resist the emulator being used for outright piracy and cheating. Of course, when you attempt to emulate current-generation hardware, the debate is a minefield.
We imagine that Nintendo is watching the progress of Cemu closely, but at present it's still a long way from being a valid threat. Not only do users need powerful PC rigs, they also have to put up with severe limitations in playability. The progress it's shown, however, has certainly been eye-catching.