Honestly i think it also depends on your Petsmart. I have heard of horrific stories of neglected BP's from Petsmart and other pet stores, which I will say it is true in some areas. However at my Petsmart all of the animals are well taken care of, I purchased my ball python from there and he is a happy and healthy little guy with no problems whatsoever. I also know the staff and the girl who took care of the snakes loved them as her babies and took ridiculously good care of them. She was also very experienced with snakes so I think sometimes at Petsmart unhealthy reptiles can result from bad staff who arent very knowledgeable (who knows just guessing). Before you purchase the snake ask to hold it and examine it for signs of bad health. Dont be afraid to ask nosy questions also.
Of course there is always the argument that you shouldn't support Petsmart at all due to some of their locations taking care of animals improperly, but if this is your only option then dont just cross it off the list.