I am an aged amateur photographer who started using Serif Photoplus when I first got into digital photography, but then graduated to Photoshop until Adobe moved to their software rental approach, when I re-tried Photoplus.
I found it adequate for my needs, but my no means as powerful as Photoshop CS4 which I had been using.
After a short time using the Affinity Photo public beta I find that it is at least as good as Photoshop for my needs, and in fact is probably better. For me, the single biggest advantage over Photoplus is the accessibility and useabilty of channels, particularly in being able to easily produce intricate detailed masks for such things as leafy branches or complex architecture against a sky.
Although my own interest is in photo editing I get the impression that Photo is equally competent in the more creative areas of digital artwork, and so for me it appears to be a winner, and we're in the early beta testing stage so far.
Well done Serif.