It's $70 for the DS by itself. You can apply it toward whatever you want, but the smart money is using it to upgrade to the Lite.
Actually, its $70 if you put it towards a DS Lite. Otherwise its just the regular $50 value for your DS.
Folks, the original poster is correct. Through the 11th, there's an extra 20 bucks trade incentive ay Gamestop/EB on 360, Xbox, PS2, DS, GC, and PSP. It has nothing to do with what you choose to purchase.
Also, FYI, Gamestop has finally begun giving discounts to customers with EB cards and vice-versa.