This is not a review, but just a few thoughts from my first day shooting with the K-3. I got it yesterday and was glad the batteries are the same so I could put a charged up battery from my K-5 in it and get right to taking some photos. I went to an assembly at my son's school and shot the kids dancing to Grease songs (my son had never heard of the movie until I mentioned it after!). It was in a poorly lit gym. The lighting was was awful, with a weird yellow tint and not much output.
I shot mostly in TAv mode, trying to balance noise, DOF, and shutter speed.
In my hand, the camera feels great. Kind of like the K-5 but even more ergonomic. I didn't notice that it was bigger and heavier, it feels reasonable to me.
The shutter sound is like a whisper. More of a "swish" than the K-5 and no clunk like my K-x.
It was responsive and I had correction enabled. Much quicker than the K-5!
I did some NR and tried to fix the WB (it was on auto) but it's still not quite right to my eyes. All edits done in Lightroom 4.4
1/125 ƒ/6.3 ISO 2500 53 mm
1/125 ƒ/6.3 ISO 3200 135 mm
1/125 ƒ/6.3 ISO 3200 24 mm
1/125 ƒ/6.3 ISO 3200 18 mm
Then after work I took a little detour and shot a little at sunset and after.
I was shooting handheld, so I had the ISO at 800-3200. I only have this one posted.
I brought the shadows up quite a bit to get some detail back and that looks reasonably clean to me.
1/640 ƒ/8 ISO 800 53 mm
In my quick edits last night I was definitely noticing more noise at 100% as others have noted. I just used some of LR's NR to tame it, but at smaller sizes like this it's not bad. It was noticable enough in some images I had a little concern but not enough data to come to any conclusions yet. I'll probably be out shooting in the dark tonight so I may add to this as I put the camera through it's paces for my kinds of shooting situations.