Just bought this card for my 3DS which has firmware 2.1.0-4U. The site I purchased from Modchip Centralsays that the card is updated for DSi 1.4.3 and 3DS 2.1, so I'm hoping it will work out of the box.
I've also went ahead and purchased a Patriot MicroSDHC Class 10 (8GB) to go with it from Amazon.
I've also went ahead and purchased a Patriot MicroSDHC Class 10 (8GB) to go with it from Amazon.