This is the quote from official site , roughly from the google translate:
1.Improved system stability : that's to say,it will offer a more comfortable way to enjoy for users.
2. extended communications capabilities :has extend some of the ability to receive data, such as Oshirase.
3.Better network connectivity :this improve mainly for dealing with other wireless Internet access in some Nintendozon, sometimes can not communicate .
4.Added "3D images of live music," : Delivering music is "Super Mario Brothers Theme" in, O. Kondou Hiroshi was responsible for the Super Mario series composer (piano), is played by studio musicians
R4i gold official site also released the news: R4i 3DS Gold flash card works perfect with the new firmware 1.1.0-1J on 3DS it means Nintendo 3DS's update won't block the DS-mode.
Ak2i team also released the update news and their card is working for 3DS too.