This is probably the coolest truck conversion I've seen.
It's a home-built box on a new truck chassis using techniques from the boat industry. Doug and his family (five in all) traveled Europe for 16 months in this rig. Overall, it's a pretty impressive use of space.
You can also google "shachagra" for some more info scattered about as well as build and trip videos on Youtube. His rig was also featured on an "extreme RV" tv show.
That's a pretty nice setup. We are considering something similar (tailored to our unique needs, of course) for our planned full-time adventure with my wife and three kids, but we're also looking at a bus conversion or a sticks-and-staples RV. It sounds like you're pretty happy with the company that built your box, did you consider any other firms? Would you mind giving a ball-park cost for the box?