To us, they've just made the iPad Mini with a bigger screen and called it a day.
To Jony, he (And his team) will have spent months, if not years, researching materials, different grades of the same materials, different strengths tests, hardness tests, assembly methods, production techniques, meetings with metalurgists, engineers, designers, weight distrubution, stress and dynamics, fixing position variation, types of glue, application methods, colour techniques, glass technologies, coefficient of friction etc etc etc.
Thats before you get to the obvious types of jobs, experimenting with different radius of corners, different angles of the chamfer, postition of buttons, size of buttons, colours, screen sizes etc etc etc
He has lived and breathed this stuff for years, and by all accounts, he loves it.