Hi!
I have a Macbook Pro 2012 13" and 2011 15" with disabled AMD GPU. Both are using i5 (3210M HD4000) and i7 (2675QM HD3000) respectively.
My own brushes imported from Photoshop work as expected but most of the native ones are slow. Is that because of the use of Metal API functions in ASP brush implementation not used in the Photoshop brush standard? No hardware acceleration for ASP functions used in Family 1 V4 cards, only software for example?
BTW, I read about a possible Windows version in the future. I hope you take that route but understand if you don't. But if you do, take my money!

Keep up the good work or how Dean Winchester in Supernatural would have put it: Awesome!!!