GoreTex warrants that your boots won't leak and that if they don't breathe well, you can return them for purchase price.
I contacted them about returning some Garmont boots that didn't work out well in summer backpacking - moisture buildup that wouldn't readily dry out overnight.
They were very pleasant about it. Gave me a Return Authorization number and asked for a note explaining the circumstances. They did ask me about socks used, and were satisfied when the answer was Smartwool - cotton was explained as a common source of the moisture problem. I enclosed the letter of explanation, and the sales receipt, since I had it.
In a week I received a phone call telling me that the there was no defect in the boots, that the refund had been approved, and about another week later, the check arrived. It appeared to cover everything - purchase, sales tax and shipping.
+1 for GoreTex in customer service, at least in this instance. A couple of business books have remarked that WM Gore is a great company.