Wal-Mart Oil vs. Name Brand Oil

I was in Wal-Mart to buy some engine oil and I noticed that they now have a
store brand (Super Tech, I think) Fully Synthetic oil. The 5 qt container
sells for $12 something. Considering that "brand" name synthetic oils sell
for 2 or 3 times that amount, I was tempted to give it a try, but didn't buy
it in the end. Mainly because the owners manual states that you should
still change your oil at the same recommended intervals whether you use dino
or synthetics.

But I do wonder if there is really any difference in the generic brands and
the name brands. They both have the starburst symbol on the front and the
sae logo on the back, and they both say they meet the same standard
(currently SM). If they do meet the same exact standards, then aren't you
just wasting money by buying the name brands?

What do you think? Same oil regardless of brand, or do the name brands have
secret addititives that go beyond the SM spec that makes their oils better?

Sid