Retro, sort of
Samsung's revised the midrange NX model's design with a more retro two-tone look, but the effect is ruined by the lenses, which have a much more modern feel.
Now in white
The midrange camera will now be available in a white-and-silver version as well.
Tilting OLED display
Samsung updated the camera with a big, tilting OLED touch-screen display.
There are a full set of direct-access controls that you can use instead of, or in addition to, the touch screen. They're redesigned from the NX210: the back dial is gone, replaced by a five-button panel, and it's got a bigger thumb-grip area. On the downside, the record button is very flat and in that awkward area on the right shoulder. That's the same place it is on the Sony NEX-6; hopefully, this isn't the start of a trend.
Like the NX1000, the NX300 now has a button to directly invoke Wi-Fi; in the NX300, it's user-programmable for selectable connectivity options. The grip is also slightly larger than the NX210's.
45mm 3D/2D lens
A more expensive version of the 45mm f1.8 lens announced last fall, this one is switchable between normal and 3D.
Dual apertures, in conjunction with dual exposures, create stereoscopic 3D shots.