Very nice job, thank you.
I have a couple of suggestions for v.2.
Instead of copy / paste, use "duplicate". Might not be a big deal for small test files, but as you work on larger images you'll want to avoid copying large amounts of data to RAM.
For adjustment layers, the automatic layer mask is an option (on by default). So if you create an adjustment layer and don't get a mask, check the layers palette options and turn on "Use Default Masks on Adjustments"
