The thing is, the the 2.6 is equivalent in power to the fastest quad core processor for Intel Core i7-3940XM, which is amazing in its own right. Can't really say you arn't getting what you paid for, though I agree it should be better... even at 7 hours at the very least.
----------
I hope there are more guys, and girls that are getting around 11 hours.
I'm trying to find the post of the guy who is getting amazing hours even with the 2.6. This guy might want to get an exchange at the least.