Hard to tell, as I don't know how "new" they really are, compared to what you buy at a place like mf.com or sweetwater. Perhaps someone else can weigh in, but I have just gotten tangled in some pretty sneaky schemes in the past regarding ebay, so I really only sell stuff on there now.
Its obviously worth it to me to buy new, as I wouldn't buy any other way (unless its through this board, where people are generally good about not selling garbage), or I am buying it from someone I know. Just my experience though - Ive bought some electronics used on ebay that ended up fine. Just didn't happen as often as the times where the stuff broke, so it stopped being worth it.