Brand of Gasoline

Since gas is through the roof, and we are all looking for ways to save a buck, does it matter what brand of gas you use. By that, I mean, is Racetrac, Raceway, or Wal Mart gas ok, or should we stick to the BP's, Conoco's, Exxon's, Shell's, etc. in our Nomads ? I've always heard that the "off brands " have neither the quantity, nor quality of detergent additives as the "brand" name gasolines, so there is a potential fuel injector clogging problem. Can anyone shed any light on this fact or myth ?