I flirted with the Pentax K7 this month and I thought some people might be interested in what I found. I got a fantastic deal for a new K7 + 18-55mm for US$855 with free shipping and no tax. I had been giving some thought to getting one to try out so when I saw that deal I jumped on it. Sadly, I returned it yesterday. The only reason I returned it was because compared to my A700 at ISO 1600, 3200, and 6400 it was worse. In all other ways that I care about it was a very nice upgrade from the A700. A big bonus is that it was smaller so for travel that would be very welcome.
I shot 3 raw shots in my hotel room a few days ago with the K7 and A700 and ISO 1600, 3200, and 6400 (K7 v1.03, A700 v4, both with high ISO nr off). I used the meter readings for both and got similar histograms. The first thing I noticed is that at ISO 1600 the K7 needed a half stop more exposure and at ISO 3200 and 6400 it needed 2/3 stops more exposure than the A700. Since I only go to higher ISO settings when I need a faster shutter speed this immediately was a problem. Even with that additional exposure I discovered that the K7 had significantly more noise than the A700. I tried both ACR 5.4 and RawTherapee 2.4.1. RT was better, but better for the A700 too. I also tried Neat Image on the K7 images and with careful work improved them a bit, but it also improved the A700 images. Then if you consider that I really should compare the K7 ISO 1600 to A700 ISO 1200, K7 ISO 3200 to A700 ISO 2000, and K7 ISO 6400 to A700 ISO 4000 the K7 looks even worse. Just to reiterate, I am only talking about high ISO.
The camera and its features are really wonderful. Note, for other people very fast AF or fps or something else might be really important. I checked the things that were important to me and the only bad thing I discovered was the high ISO.
If the K7 had the Kx sensor or even the A550 sensor it would be really nice. For me though, I find that when I travel I use ISO 1600 and higher from time to time for people at night on the street, etc. so it is important. It sure was hard to return it, but I decided that even if I kept it I would end up picking up the A700 in preference for a trip and also that with the poor high ISO I wouldn't be motivated to buy any additional Pentax mount lenses. Maybe a K7 update will be out this year though and I bet Pentax addresses this one big shortcoming.