I really hate [edit: the necessity for something like] this. I deeply disagree that Photoshop has better UI than GIMP, it's just that GIMP is no professional's daily driver, you were paid to learn Photoshop; and whenever you learned any technique, you learned it in Photoshop. Clinging to Photoshop UI (which is completely arbitrary and bizarre) just supports Photoshop - you're taking a vacation instead of making a move.

That being said, the comfort that millions of people have with the Photoshop interface is in itself an institution, and has to be respected as such (imagine the collective number of man-hours put into learning it.) I don't know what the answer is. But the worst possible outcome is the Firefox outcome, where GIMP ends up chasing Photoshop rather than remaining its own thing.

Just, please, try to get out of your head that GIMP's UI is bad. It's not, it's just different. Don't think of it as a knock-off Photoshop. Deal with it on its own terms. Use these Photoshop skins as a transition rather than a destination.

That means I might have a problem with this approach, just because it doesn't allow for a easy switch between classic and Photoshop UI. It's actually annoying to switch back and forth. If it catches on and brings more users to GIMP, it will become the interface, and leave GIMP vulnerable to IP attacks.