As video games have become a significant part of our culture, emulation has become a critical tool for preserving it. Thank goodness for projects like this one.
Well, on the plus side, the PS4 doesn't use the Cell processor, so an emulator doesn't have to waste most of the CPU resources modelling the behaviour of that thing. On the minus side, the PS4 onwards (and equivalent Xboxes) have very fast shared memory; it's really cheap for the CPU to read the GPU framebuffer on consoles for post-processing effects, whereas that's a massive hold-up on PCs. And just about every game does that kind of post-processing, whether it's for colour adjustment / tone shading / anti-aliasing. Might just be one of the things that falls to brute force over the years, but it'll probably be far too slow without a clever solution in the mean time.
I love the fact that on the two ocassions I decide that I should get a previous-gen console secondhand once the current-gen one becomes mainstream enough (PS3 being the previous one), I come to know of an emulator for it. What I love even more is that its the same person coming up with the emulator both times.