While still waiting for my new (hopefully problem free) NX300, was using the faulty one to get used to the camera...
This is when I noticed some major shortcomings in the NX300 videos department.
The previous cameras had their own video mode dial option, while the NX300 has no dial but inherits your settings from your current manual/PASM mode settings, which isn't a terrible thing in itself, BUT:
1) There is no longer any manual ISO mode setting for video! You get auto and that's that, with no way to lock it! This should be easily rectified in firmware, so hope you do that.
2) You don't get a proper 16:9 preview until you hit the record button! This one could be rectified by placing a video preview icon on left side of screen.
I steered away form panasonic MFT/m43 cameras because they took away manual video control (unless you paid silly prices for GH3), and now Samsung appears to want to do the same.
Please do not go down that road! Be better than the other manufacturers!
Since firmware V1.1, manual ISO is now available in full manual mode for video, but still not for aperture/shutter priority, nor program AE. Heading in the right direction now.
But we still need a way to get a 16:9 preview of what will be recorded.