I picked one up yesterday. Note that you can get DS's for $109 + Tax (that's the price IIRC) at EB and Gamestop, but all the ones around me tell me that all their stock is used instead of refurbished.
Refurbished means the systems went through QA with the replacement or fixing of any defects as needed, used means exactly that, they received the unit, might have tested it, but basically cleaned it and wrapped it up. You are almost always better off buying refurbished over used.
Edit: I forgot to add, shipping is indeed free, but they tack on ~$5 in "handling fees". Cheesy, but still not a bad deal by any means in my opinion. I was going to wind up getting the Mario Kart bundle, but red isn't exactly my favorite color. (On that note, it was pretty short-sighted by Nintendo to only make what would obviously be a popular bundle in only one color, but what can you do.)