[pmontra]

And never ever be able to seat on a standard chair or travel in a car? Probably not.

I would think about how to carry on common tasks with common items such as seating, sleeping, wearing clothes, etc. Perhaps 4 arms would be better than 3 given our symmetry but they're going to force the owner to use so many specially built stuff. I guess two are going to be optimal for a while.

Or attach the extra arms to a hexoscheleton and wear it only when needed.