it finally downloaded. I decided to leave it on overnight and hope for the best and when I woke up the console was off. turned it on and the update had downloaded and installed, no idea how long it took, but before I went to sleep, the timer read 3hrs, 54mins.
terrible service from nintendo. to contrast, I received my ps vita today, turned it on and found my network within minutes and downloaded its various updates within 15 minutes. a quick check through the menu showed it was using my full connection, the problem with nintendo updated definitely lies in their servers / infrastructure.