I'm very happy with my purchase from r43ds.org On April 18 I bought the r4 3ds rts card for my 3ds XL. The card was shipped promptly and the package arrived in just over 12 days in total. I had some trouble setting it up and getting it running, but a quick email to the CSR over at the site fixed things right up when they took the time to send me a step by step email on how to setup the card, and to diagnose my problem to find out where the error was. As it turned out, it was me putting the wrong firmware on the card.
As a side note, my cousin ordered one on April 15, and it just arrived to him 2 days ago. So sometimes, depending on the post office, it can take longer. His cards were shipped 3 days after he ordered, and mine were sent 4 days after I ordered, and mind came in sooner.
I'd recommend this site to anyone looking for a real genuine r4, 'cause there are way too many fakes out there, and site peddling obsolete versions of this card.