Thanks for posting this!
I've never ordered from Go Hastings before, although I have browsed their site a few times. They seem to have reasonable prices for used items, but everytime I've wanted to buy something from them, their shipping charges kill the deal--sometimes the shipping costs more than the actual items I'm ordering!
And it looks like the code will work for orders less than $20--I was able to apply it to an order for $13 worth of stuff.