I've had brief email exchanges with Gus Mueller; sent him a few remarks together with a link to this thread - so hopefully any comments, observations, suggestions made here will also be picked up by him.
re Acorn – just a few quick initial observations :
- There's a tool named Select - quick, simple way to create good layer masks. Masks in Acorn can be feathered with a Gaussian blur in the non-destructive filters - you can go back and refine the blending as you wish, combine any number of filters including all the colour controls in a non-destructive manner.
- No easy way to feather the Eraser. You need to select a brush , change it's blend mode to Destination Out, and it'll act like an eraser – alternatively hold down both the option and command keys when using a regular brush and it will act like an eraser.
- It's possible to align layers but the way is slightly arcane. Hopefully there will be a simple Align Layers menu command to come. Currently applies to shapes only.
- There is no History. The only 'destructive' controls though, at this time, are Levels and Curves.
Interesting program in and of itself, but particularly when combined with Lr.
Masking tool is called Select. Instant Alpha creates cut-out directly on the layer.