After 5 mostly happy years with a combination of Panasonic and Nikon cameras, mirrorless and DSLR, I've made a sudden move back to 100% Nikon and DSLR. Just in case others are interested in what and why, here are my thoughts around this theme:
While I have been living happily with 12-16MP for all these years, a need for more pixels have arisen. An important client flagged this need more than 6 months ago, and now it's becoming reality. I could have moved to Sony, and for a long time, that looked like the most viable option, but the lack of native lenses and the fact that I would need at least two, probably three new bodies if going for that option, made the investment unbearable. Also, I didn't like the ergonomics of the first versions of the A7 bodies. Nor did I like the shutter noise. The A7 II is of course a much better camera, but the others still lag behind.
Samsung was another alternative, but although the NX1 looks amazing on paper, it's untested, as is Samsung as a pro level supplier. Nikon or MF were the most likely candidates.
As happy as I have been with m4/3, there have been situations when I've attempted to pull my hair out. Blown reds in polyester fabrics is one that occurs for sports as well as with industrial settings. Software corrected lenses that don't behave as predicted is another (pocketable lenses are convenient, but there are limitations). Super advanced and very fast AF-S is great too, but when the camera disagrees with me and changing settings are fiddly, I lose shots.
All the electronic wizardry is fine and very helpful, but sometimes, it detaches me from the process, physically as well as mentally. Image quality suffers in situations when that happens.
When the G1 was launched, it was a little camera revolution. Anything after that in the mirrorless market has been evolution. Fast evolution, but still evolution, like improved AF, improved viewfinders, more and better lenses, larger sensors etc.
In my head, the DSLR bodies have been the dinosaurs, the ones that would become extinct sooner rather than later. And they will. Eventually. But... the DSLR bodies have developed too. Sensors have obviously become better, video capabilities have improved to a degree that they can compete with mirrorless cameras, better than some, worse than some, more and new features have become available in smaller, cheaper bodies. And so on.
When summing up, I've found that the best DSLR cameras have indeed kept the distance to the mirrorless varieties rather constant. There's a huge difference between what one could get for $2-3,000 5 years ago and what one will get for the same amount today.
Cameras cost money, good cameras cost more money and good lenses too. Staying with Nikon would mean staying with most of my old lenses, lenses that have little monetary value but will still be useful for many years. Good native lenses for mirrorless aren't really much less expensive than their DSLR counterparts, regardless of format. With mirrorless, I can save money using legacy glass, but with zillions of good Nikkor lenses available used, that's the situation with a Nikon camera as well.
While no digital camera is a healthy financial investment, prices of cameras that are replaced more frequently will obviously suffer the most. The D300 that I bought slightly used for $1,000 6 years ago can still be sold for $3-400. The GH1 that I bought for a similar price a year later can hardly be sold at all, and while the D300 still seems to be in top shape, the GH1 has had assorted electronic failures.
The GH3 and GH4 have batteries about the same size as what most Nikon cameras have. Still, I can only get 4-500 shots out of one charge, while a typical Nikon DSLR will give me 2-3 times as much. Most other mirrorless cameras have tiny batteries that last even shorter, and although one can always bring spares, I don't need more logistic challenges than I already have. With 2 Nikon bodies, 2 batteries in each, I know that I have power that will last a long day at the race track or an event. Peace of mind
Sooner or later, Nikon will launch an FX mirrorless camera. I see the "1" Series as little more than a test bed for mirrorless technology, and expect a camera that is somewhere between a V3 and an F4 within a year or two. I also expect that camera to retain full functionality with all my AF-S and Ai/AiS lenses. I might be wrong, but I doubt it. The people at Nikon know where the market will be heading in the future.
Video quality of the latest Nikon bodies is very, very good. The specialist video websites always find something to pick on, but in reality, Nikon is now up there among most of the good mirrorless cameras, with the exception of A7s, GH4 and NX1. If I need an external viewfinder, one can be attached, as can external monitors, recorders, microphones etc.
What made me make up my mind... fast
When the F5 was Nikon's top model, that was all Nikon users needed. It was used for any kind of photography; sports, landscape, portrait etc. The backup for an F5 was another F5 or an F100 for those who wanted a smaller body as well, but the features were the same and the film was the same.
With digital, "horses for courses" suddenly became the important buzzword. One body couldn't do it all anymore. A D1X for slow work, a D1H for speed. Canon did the same, and even used a smaller sensor for their sports camera. There were exceptions. The D2X was a nice attempt to do all, but couldn't do high ISO. The D700 was a better attempt, but only had 12MP. There was always a but.
I hadn't give these things much thought lately, and when the D810 was launched, it looked like just another incremental upgrade to me. Maybe that is what it is, but for the first time (5D/II/III owners might disagree), when I finally bothered to try it out, I had a feeling of holding a "complete" digital camera in my hands.
Image quality is great, low ISO, high ISO, any ISO, frame rate is high enough, buffer is huge, video quality is top notch and with practical features to match, the shutter is almost as silent as on the Contax RX, it's heavy, but lighter than the D700. I can use this camera for anything.
When I was offered a hardly used copy $600 under the local street price, there wasn't much to consider any longer. It's all I need in an acceptably sized package. It's a camera that I'll use for many years.
I'll miss the weight and size of the GH3 and lenses, and I'll miss the incredible Zuiko 75mm that lived on my camera. But I've found that the operation of the D810 is as fluent as with any Nikon in the past. And the files are to die for, which is what counts anyway. I'm still strong enough to carry a few extra kilograms. And when I'm not, there will be a mirrorless Nikon, a camera that I'm sure will be up there with the best... or above them.
For there will be a mirrorless camera in my future as well. But right now, I'm very happy to look through an optical viewfinder. It doesn't feature a histogram and it can't be used for video, but it's the real, undistorted world I see in there. That's a value too