What really blows me away is how comparatively little the interface has changed over the years...not to sound dense, but it looks exactly like you'd expect Photoshop to look.
(I've honestly not heard much about CHM before. Making sure to find my way there next time I manage to end up in the Bay Area)
[0] http://www.computerhistory.org/atchm/macpaint-and-quickdraw-...