My Son and Daughter downloaded the level 50 Zoroark to their Dsi-XL's while we were at Toys r Us also. Took about 20 seconds. This will only be avaialble until this Sunday and is Free. Just go to the gaming section and they had a sign posted with the instructions.
No software update required (which I was worried about) for those with R4 cards, but R4 cards wont connect wirelessly (at least not our R4i Kings)