Today Pixelmator (website) (App Store) released an update supporting the iPad Pro including 16K image support and a new palm rejection feature. There are over 50 brushes that work with the Apple pencil.
I've been working on the family Christmas card in Pixelmator on my iPad Pro for a week now. When I loaded the image in the updated version of the app, I immediately saw the benefits. I particularly like the way they've taken advantage of the additional screen size.
This update also introduces support for 3D touch on the iPhone 6s and iPhone 6s Plus. Force touching on the Pixelmator icon opens quick action shortcuts and inside the application they use 3D touch support to bring touch sensitive painting. Varying the pressure on the screen with your finger changes the thickness of a brushstroke.
Over the past year I've increasingly done my more complicated photo editing on the iPad. This trend will only continue with this new version of Pixelmator and the arrival of my Apple pencil.