Yes, NX1 delivers gorgeous 4K video, especially with the Samsung 16-50 lens. I have this combination, and I'd have no hesitation in recommending it for any 4K project with your kind of budget. This combo is a bit pricey though ($2,799 as of today), but you could get the cheaper $1,499 set instead.
The workflow is great too. You can play your movies right out of the card with players like Potplayer (on Windows). If you like it, transcode to ProRes with FFmpeg (I use the Rocky Mountains front-end) and edit in your editor of choice, which you'd want to do anyway even with H.264 footage for easy editing.
I have the 6D too. It's great for photos, but for video, you'll need to watch out for aliasing and moire, which can be pretty bad. OK if you're doing narrative work, where you can control what's on camera; but for documentary/event kind of work, you will run into problems at wide angles.
Looks great, and the music is giving it gravitas. You can see some banding and blown highlights in the skies, but nothing too distracting. I'm not sure about the teaser edit though, seemed a bit random.
So sorry to hear about your bad experience, Sophie. Yes, RAW can be a major pain and is not always an automatic choice due to the reasons you cited, especially for low budget films. There is a good discussion by experts on when it would be appropriate, check out http://www.cinema5d.com/do-we-really-need-raw-video-dan-chung-clinton-ha.... One view was that it makes most sense in scenes that need a lot of latitude in grading.
I've had a 6D since late 2012. It has awesome low light performance and the benefits of FF (shallow DoF you'd want for your work), but it also has pretty bad moire and aliasing. For short films, you can control it; but for the doc and music video work, you're going to see moire if you're out of luck. If you do get the 6D, absolutely use the Technicolor Cinestyle profile and settings.
To get a rough idea of the kind of quality you can expect on your music videos, check out some videos I shot of a Diwali program last year on YouTube at https://goo.gl/mbCz6D. Not quite music videos, but they should give an idea.
Not sure I agree, Ed. For your particular film, may be any camera would have sufficed. But then I'm not sure you really tested the strengths of NX1 relating to resolution, skin tones, DR, low light, and the like, so it doesn't really mean much. Kind of like concluding looks aren't important after seeing Charlize Theron in Monster. If you shoot a film that does test the NX1 strengths, I'd love to see it (not too many NX1 films out there that do that).