I’ve just updated my 3DS a few minutes back and am still investigating (the new firmware update is live) but from initial reports on Twitter and around the web it looks like the portable now supports ‘Accomplishments’.
These system level critters apparently mirror the 360’s Achievements and the PS3’s Trophies, with some users reporting a burst of Accomplishments from the Mii Plaza section of the home screen.
I’ll dig around some more, but it currently looks like the system might currently only be activated on the Mii Plaza itself. If Nintendo can roll these out across games (especially the retro stuff) I’ll be super happy.
The firmware update also adds 3D video recording and some other new features.