I had a great relationship with my Panasonic GH2 but after 3 years our ways parted a few days ago. The GH4 took her place. We have a lot of familiarizing to do before our relation will reach that same level of affection and confidence but our first 4K production is a fact, however brief and frivolous!
For good measure, I picked up a Panasonic Lumix 12-35 f2.8 as well, which is the lens to have for a documentary filmer. I have to grow into this lens as well- it doesn't have that same organic feel as my favorite lens, the Panasonic 20mm 1.7
Shooting in 4K has a lot of consequences- and shooting in 4K is what you buy this camera for. A big drawback is the narrow field of view. The cropfactor on the GH2 was already 1.82 but shooting 4K increases that factor to 2.2. In other words, 12mm becomes in effect 26mm compared to a full frame camera. That is not very wide when you're shooting in a tight spot or indoors.
Another reason why you'd want/need to shoot 4K is because it produces great Full HD pictures, better than shooting Full HD right from the bat. It sounds absurd and that's what it is, but downsampling the 4K image to full hd produces much cleaner and richer images that shooting 1080P. And 4K grades much better than Full HD.
But the 4000 dollar question is: does downsampled 4K look better than 4K itself? Stay tuned for more and in the meanwhile, enjoy the short boatride.