My brother has one, which he got from my Dad, who bought it from his father back in 1960.
Grandpa built a new house in about 1953 and he used the ShopSmith Mark 5 (brand new at that time) to make a few simple furnishings, gadgets and gizmos as well as cutting all of the finish trim for the interior. In 1960 my dad started building his first house and asked to purchase the ShopSmith since grandpa was done with it. He had the table saw, disc sander, jointer, drill press, lathe, and horizontal boring machine setups. Sadly, he did not have the bandsaw or jigsaw, but I used it an awful lot when I was growing up. Eventually he purchased a separate table saw, but the ShopSmith still saw quite a bit of use in its other capacities.
A couple of years ago Dad moved into an assisted living facility so the shop tools had to go. My brother had already taken over the table saw, which didn't bother me, as I bought one very similar to it a few years ago. I already had a drill press and a small disc sander so I really had no need for the ShopSmith, so I let my brother take it as well. It's still there if I need the use of it, and I don't even have to store it!
They are wonderful machines for those with limited space, and changeovers take place quite quickly, so they definitely have their place.