Im happy to report my experiences at JoAnn's have mostly been good, and have never been shorted on yardage. If the bolt is near the end I'll usually ask how much is left before deciding how much to buy; if there's say 1 3/4 yards, I might request 1 yd, and ask for the still-attached remnant too, which is half off. On my last visit the young lady at the cut table told me that the last 1 1/2 yd of a bolt is always half off, so I paid only 25% for that whole piece because it was on sale at 50% off, then half off that!
I AM very careful of fabric quality, since some of their stuff is very nice and some is junk. My closest LQS is between home and JoAnn's, so I try to stop there first and check out the sale racks, where I've found some beautiful stuff for $4.50-5.00 yard.