My first K-1 images was taken Oct. 3, and I have 714 keepers in my library taken with the camera. The last one taken today has a shutter count of approximately 6,400 images.
I don't know whether to go positive or negative first... maybe just topics. If you missed the dynamic range of the K-5 when you moved to a K-3, you get it back plus another stop on top of that, almost 15 EV.
For images like this one, you can never have enough dynamic range. K-1 image
However, the K-3 wasn't all that bad, the thing is your display of DR is limited by your output device, so while the DR may add detail to your image it's unlikely the final image will look a lot different.
K-3 sunset..
The advantage is definitely with the K-1, how much it's worth to you to have 15 EV DR instead of 13, you may be disappointed.
The K-1 is good up to 3200 ISO, I really don't like the K-3 over 1000 ISO, IMHO it's more than a stop.
For walking around, there is nothing better than my K-3 with an 18-135 on it. There is no way you can avoid using two lenses for that range on a K-1. Not only that the 28-105 is about the same size as the 18-135, so you're going to be carrying a lot of extra weight for the same capability. And the 28-105 is the only modern DC motor type lens. If I have one big issue that's it. There simply is not enough "standard lens" type options. There should be a cheap kit lens sold as a throw away with the camera, a mid range like the 28-105, there should be at least two in that category, like the 16-85 and 18-135 on APS-c.
The other issue here is the weight. Long glass is prohibitive for the same capability.
For the same field of view and ƒ2.8, six pounds and massive compare to easily hand holdable. DA*200 on K-3, Tamron 300 2.8 on K-1.
Shooting my feeder denizens... for the birds I can walk up to, the K-1 gets me better images...
For the skittish birds where I have to stay in the blind, maintain some distance and where any noise will spook them, the K-3 is definitely better. And with K-3 and burst, buffer and AF being what it is, the K-3 is a joy to work with compared to a K-1 going after the same type of image.
There are some issues with the K-1. It's harder to get the images you want, but they are better when you get them.
I have shots like this, taken with the 50 macro @ 3200 ISO, in near darkness, and flash was truly not an option. I wouldn't even try this with a K-3.
So in essence, even with all the issues, the fact that the 2.8 glass for it is going to set you back 6k if you go for all of it, and there simply is nothing for it in less than 2.8 glass I still like it. The old FA 20-35 ƒ4, which is really what I'd like has become as rare as hen's teeth. No one is parting with theirs. And there's nothing coming on the lens map.
So the buy in to make all use of the K-1s capacities 2k for the Camera, $1600 for the 15-30, 2k for the 70-200, 1.2k for the 24-70, an no reasonable options to replace them. You're looking at $7000-$8000 without another 2k for the 150-450, to get you the capability you have with a 55-300. Just to have the same capability you have for your K-3, and probably a less than 2.5k investment. Now there's s source of frustration.
All that being said, my K-1 is my current "in the hand, walk around" camera. My K-3 is on the holster with the DA*200 with stacked TC in case I come across some wildlife.
Some recent images...
These are all marginally better than the K-3 images would be. It's twice the sensor area for twice the price, but it isn't twice the IQ. The maybe 33% extra resolution comes at a disproportionate price. And paying it means you have to carry heavier gear and work a lot harder to get what you want. Plus you'll take it places you shouldn't. Places the K-3 would actually be better, just because you like it. IMHO for the first little while until you get disciplined about taking the right camera for the job it's going to cost you IQ in some images where the K-3 would have been better. Once you get used to it and the "shiny new toy" thing is over, it's a wonderful tool. But unless you're rich, it's not going to be like APS-c where every lens I own is top of the line, for the purpose for which I bought it. There is going to be some gnashing of teeth, when you should have brought your K-3 and Sigma 8-16 and all you have is 28mm on a K-1 because you brought your "landscape" camera. In that case you will come home without the image you could have had. Instead of a possibly great image. Sure you can say, well bring your 8-16 and your K-3, but, on a given hike, I can only carry so much stuff.
Honestly for a guy like me where the ideal kit is two lenses, the K-1 is bad idea. But the allure of the images when you nail one is also exhilarating. It's like gambling, my odds are longer, but if I win I've got noticeably better. And also like gambling, it hurts when you lose.
On a lighter note, the tilt screen is really cool, and Pixel shift isn't worth paying for. Of the images i've done, where I compared PS images to a normal shot on the same tripod set with a 2 second delay, the PS images are better maybe 20% of the time, 80% of the time the non-PS image is better, and it's a lot of work for not much reward.