UPDATE: The eShop is back up and running. There are no obvious changes, though. Also, it looks like the Wii Shop and DSi Shop were also down for maintenance today.
Currently, the Nintendo 3DS eShop is down for maintenance. Perhaps this is to prepare for the Ambassador Program, or maybe it is something else. We will just have to wait and see.
Error Code: 007-2503
Nintendo eShop is currently undergoing maintenance. We apologize for any inconvenience. Please try again later.