I'm having bad luck with grey items, when it goes to vendor it always leaves behind some grey items and occasionaly some blues/greens. It usualy gets them the 2nd time around, but ALWAYS leaves grey items behind. I've noticed a build up of a good 20 grey items in my bag that arent selling.
EDIT: Ok so its not that bad, it does leave behind grey's (And a few greens that are on protected list), but it usualy sells the grey's the next time around, at which time it may leave a few grey's again and so on and so forth.