You can sell all your stuff, drain the merchant, then simply swith and get a new batch of goods (and money). Also it allows you to 3x re-roll items, and unlike save/reload you can even profit from buying all 4 rolls that end up being presented to you.
Also, and this is not the exploit side, it can be very annoying if you want a particular item that vendor has, talk to him/her with the wrong character and bam... the item you wanted is now gone.
