I got a refund on a kit this summer - the AK 47, which I had brewed twice before successfully. I explained that I followed everything to a T this third time and ended up with very low OG and the kegged beer tasted lighter (and worse) than the worst of the "light" beers on the market.
They didn't bat an eye, thanked me for letting them know, replaced the kit and the Wyeast smack pack that went with the kit.
I also had a problem recently with a keg part - took it back and they also replaced it (wasn;t even asking them to, was just asking what the problem was - they said it looked defective, "here's a new one at no charge.")
I live in Mpls and am in the store pretty often (with some pretty mundane questions), but am always treated well and I think they live up to what they say.