Before I bought my TAG I looked at the ones at Costco and then I spoke to one of the authorized TAG dealers in town. According to the Dealer TAG will not honour the waaranty if the Warranty book is not stamped by an authorized dealer. Since Costco is not an authorized dealer if there is any waaranty issues you have to take them up with Costco.
As many people have said here Costco has good return policy and if the manufaturer is refusing to honour the warranty I am sure they will take care of the customer.
I didn't buy the TAG from Costco because they didn't have the model I was looking for but if they have what you are looking for go for it.
