i've not had any issues with refurb cards. they are usually gone over by the company that makes it and then re-certified to be in working order. they usually have a warranty included so there is really no risk involved with buying them. great way to save some money or to push your budget into a higher level card.
if it does not have a warranty attached by the company then i would avoid it. if they won't back their work, no reason to trust them. keep in mind quite often when you buy a new card and have to have it serviced, you often get a refurb back anyway.....
i have also bought open box cards from newegg from time to time but many shy away from them as they often come without all the fluff inside the box like manuals, driver disks...