In honor of New Super Mario Bros 2 being the first 3DS game to be released both digitally and via retail, Nintendo is offering a small bonus for digital supporters. If you purchase the digital version and register by 9/20/12 you will earn 100 coins on Club Nintendo. This might not sound like much, but thats twice what the retail version gives and is 1/6th of the way to platinum status.
While this is a great deal, Japan also received Donkey Kong as an additional bonus. Sadly that has not been announced for US members. Thankfully there is a lot of time left, though we never got the Kid Icarus promo either.