i have used a 4GB sandisk class 2 with my dstt for over a year with no problems. recently i use an 8 GB sandisk class 2 with my ak2i also with no problems
like he said... he wants it as a backup card, so most likely he has 1 or more other cards. i have one as a backup now that i have an acekard 2i
plus they are only around $5 off DX, why wouldnt you get one....
if you are planning on getting a DSi, I recommend an Acekard 2i or wait adn see how the supercard one i is. IF ur sticking with a phat or lite get an Acekard 2.1