So just got back from my east coast (NYC and Boston) trip. Here are my thoughts:
I took my K-1, 15-30, 43mm, 77mm, FA135mm, a couple spare batteries and the charger. All fit comfortably in a shoulder bag
The K-1 + 15-30mm was my walk around combo and I took about 75 percent of my shots with that combo. It was a little bit heavy but no problem with my optech bandolier strap. I wouldn't want to walk miles with it around my neck.
The tilting screen was invaluable! I took shots from all kinds of weird angles that I wouldn't have attempted without it. It was plenty bright enough when I turned it to daylight +1 mode. Also manual focus was a snap with magnification. Love the rear screen
Probably the only negative I experienced with the camera was that its wake up time is slow compared to the D810. Most of the time it didn't come into play. But there were a few times where I missed a shot because the camera took a bit too long to wake up
Note this isn't start up from being off, in that case it's quite fast. This is when the camera is On but sleeping. That was frustrating. Otherwise it was a pleasure.
Now...the lenses.
The 15-30mm is awesome. Love it. It is not small by any standard, but it was great. Only drawback is that the hood is too small and you can get some flaring. I used my hand to block out stray light.
43mm of course was great. Small and I really liked the IQ on FF. It is not a fast focusing lens though.
77mm is really sharp from wide open. It renders very beautifully and the bokeh is delicious. But unfortunately the purple fringing is definitely an issue at anything wider than f4 or so.
FA135 I used a lot for city scapes. This lens is great if you know its personality. At infinity wide open, it is soft and you are going to get a purple glow making it almost unusable in that situation. But for portraits at closer distances (not infinity) it does really well. And it worked really well at f8 for the cityscapes. It was really sharp.