I've recently discovered Affinity as an alternative to Photoshop, Illustrator. I was looking to replace it at work and rather than paying £50 a month for CC, I can pay £50 for the software. I've been using it on my Mac at work and it's been an absolute dream to work with. In fact when it comes to working with large PSD's I've found it performs better than Photoshop.
However, Windows is a very different story, it's so sluggish. My computer is very powerful, i7, 8GB RAM and AMD R9 Fury. When moving layers there is a second delay before it actually moves, when applying Adjustments there is a second delay before it updates. It makes the application unusable as I feel like I'm fighting with it to get it to move layers, sometimes it's so delayed I get lost in the layering system.
Adding a layer inside a layer (nesting) takes about 2-3 seconds.
Moving layers feel sluggish, just everything feels slow.
I haven't tried Affinity Designer yet, however the slowness of Affinity Photo on Windows 10 is stopping me from moving from CC as I use a Windows at home and Mac at work.