It's a great concept. You don't have that fancy roofline that does nothing but create esoterics. What you do have is a place to store everything right outside the barn door side while not cluttering up the interior of the living space. The roof never needs replaced, the siding never needs replaced. The roof of the living area is not exposed to the sun making utilities cheap.
We will never leave where we live now, but if it were an option back in the day, this is the way we would go.
I definitely like this idea if/when we ever get some land. I'm not sure I could convince the wife to forego a 'traditional' home, but having a giant attached shop and garage area would be awesome to me. Could even partition parts of it and would be easier to heat/cool sections, have a paint room, etc. I'd want to make sure it was solid construction all the way around, but man... I could definitely live in a setting like that.