Dave has it right, and articulated it quite well.
Extra layers of plastic are the old way, and weren't so nice even back then.
We think the balance will increasingly favor virtual legends for special purposes, which is already the standard of practice for smartphone and tablet UI's.
BTW - re: Colemak, we continue to be impressed by the logic of these users, and are becoming more convinced we should manufacture custom keytop sets for these folks.
We're thinking of posting a proposed layout for Colemak in a few weeks to let forum posters weigh in, and have an influence on the design details.