Mine arrived today. I don't have a lot to say on the matter yet, as it's raining here today which limits my ability to put the camera to any interesting use. (It's waterproof, I'm the one avoiding the rain ) I'm also going to ignore the photographic aspects of this camera entirely, as I'm not sure there's anything that merits comment. AF system tests will have to wait. It came in a super nice box. Maybe that seems silly but the whole thing is matte black on the inside, and packed neatly with just a few items. As many have said before, it's outwardly nearly identical to the GH3. Indeed the only real difference I'd notice if blindfolded is the heavy locking mode dial, which has very positive detents. It's considerably stiffer than I'm used to, enough that I'm not sure locking was necessary. That's probably a good thing. There's also a slightly different viewfinder; we'll get to that. The same exact battery and charger are in use between the GH3 and GH4, which is also welcome and will faciliate A/B camera setups. And overall, the camera is very well put together while still very lightweight. Unfortunately they kept the bad parts of the GH3 body too. The thumb wheel is still obnoxious to use, due to being wedged into the handgrip. Still have the annoying PC sync socket with screw cover. The camera also has the same rubber sealers seen on the OMD cameras and the GH3, so if you found those annoying, no luck here. Turning the camera on doesn't yield any surprises. All of the software seems to be pulled directly from the GH3, just with more options. A lot more options. I'm not one to rely too much on the manual, but there's a ton of different ways to configure this camera and not all of them are obvious. The nice thing is the basics -- 4K recording, peaking, zebras were easy to get set up. I did notice that the camera does not allow you to jump into 4K record mode from photo modes; hitting the record button will always yield 2K. Sharp, stunning, sky high bitrate 2K, but 2K nonetheless. Jump into manual movie mode, however, and the camera gives up the goods. I haven't yet tested 200 mbps recording (2K only) but my Sandisk Extreme Pro card (UHS-1, 95 MB/s) appears to be sufficient to record 100 mbps in both 2K and 4K. That's a relief - have you seen the prices on UHS-3 cards? Record time on a 16 GB formatted card is 20m26s, in 24p 4K. The screen is super nice, but more welcome is the extremely nice viewfinder, which seems to have gotten a wider eyecup and a longer eyepoint. As a glasses wearer, this is a huge improvement for me. I still start to lose the corners when you move off center, a problem I've had with every Panasonic camera I've ever used. But it's less than ever, and I don't think it's particularly different from my A77 in that regard. There's a low sensitivity setting on the eye sensor too, which is must-have. Also, the LVF toggle button now shuts off auto-switching until it's held to re-enable. Clever. Like the GH3, there are more function buttons than I can find functions to assign to. Audio levels are on screen, gains are now in dB instead of "magic Panasonic scale", and auto-gain can be disabled! My E-M5 is increasingly looking like a toy next to these bodies. There's a touch screen on board, which is not my preferred method of interacting with a camera but it seems to work fine. There are a few functions on there (one-shot AF in MF mode, for example) that I'll probably map to function buttons, if I can. The camera has three custom modes on the mode dial, like the GH3. As for the actual footage? Sharp, rich, with wide flexibility in color profiles. The addition of two explicit Cine profiles (flattish, and super flat, I think) is very welcome. I'm very tired of playing color profile games on other cameras (GH2 and Sony users know these games well). The camera allows you to save custom profiles as well. You can even control the camera settings with shutter angle and dB gain, if you'd like. The images coming off the camera is now in the range where I think you'll start to see weak glass (adapted lenses, 16mm stuff, etc) become a problem. The pixel density in 4K is high enough that classic video lenses will hold things back. As far as 4K... I'm on 1080p screens and it's brutally sharp downscaled. I think it'll still look fine when I test it on the 2560x1440 screens I have at work. Panasonic video was always sharp, but this is insane. I don't know if I can go back to the A77 for video after this. For cinematic use, I suspect that we're going to have to start softening the image artifically. So that's what I've learned about the camera so far. About the only thing I could possibly wish for on this thing is phase detect (and maybe extension to ISO 100). Hopefully I'll have an opportunity tomorrow to see if the new Panasonic AF system offers any advantage for moving subjects.That quibble aside, this camera seems to be practically speaking a "last camera". I don't know what they could possibly add that would encourage an upgrade, short of a massive jump in imaging or focus performance.