Is there really any difference between different brands of gasoline?

With all the different brands of gasoline vying for our business, each stating there brand is the best and using dubious proclamations to convince us these statements are true. Such as 'Every car of NASCAR uses our gas therefore it must be best', (we didn't pay them anything to use our gas! no really! not a penny!). Is Gas, Gas? Should you just find the lowest price and go with that? Or do the various additives make any real difference in your vehicle performance?