If the pattern on the fabric is crisp and the fabric has a nice feel to it, then I wouldn't hesitate to buy it. There are shops that get 2nds, but one can usually tell when looking closely. I have learned alot about it because of hunting for fabric bargains at the Surplus & Salvage store in our area.
Try to stay away from fabrics that don't have a nice tight weave in them.
We each have our own opinions; but hope I have been of some help to you.
Nancy