Yesterdays post and the comments that followed about the Pentax K-5 coincided with a very positive review of the camera on DPreview.

"It is hard to find a negative thing to say about the Pentax K-5."
 "Ultimately, we have no hesitation in recommending the Pentax K-5 to anyone"

It does indeed look a very good camera. I've been looking at some of the samples over the past weeks and they do look very good. The high ISO samples are amongst the best I've seen, with some excellent results at ISO 6400.

Have a look at this one from the Dpreview review. Its taken at ISO 6400. It is in good light which always produces cleaner results but its impressive none the less.

I was not very impressed by the K-7 sensor which had a lack of sharpness to my eyes and very poor high ISO performance. It was made by Samsung and ended up in the NX10, where it looked a lot better though still not especially good at high ISO's. Pentax have always gone for a "softer look" Whether this is a strong anti-aliasing filter or just software I cannot say but this is a definite trend in their digital cameras. With the K-x they switched to a Sony sensor and got a lot better reviews regarding the noise at high ISO's. Certainly the samples I saw were very impressive. 

It seems that the K-5 shares the same basic sensor technology as the Nikon D7000 and Sony A55. "The K-5 captures its images on a 16.3 megapixel APS-C CMOS sensor. This is probably closely related to the hardware used in the Nikon D7000 and Sony SLT-A55."  from the Dpreview review.
This is not the whole story but the results from the three cameras do look very similar. Interestingly from my own perspective having used the A55 I can certainly testify to that cameras incredibly good performance at high ISO's.

The Pentax is slightly lighter and smaller than the Nikon, though obviously in a different league to the A55. Though I didn't like the K-7 in terms of IQ, I liked its handling, particularly with the battery grip, and it did feel very sturdy. Its fully weatherproof, with weatherproof lenses to go with it. All in all it seems an excellent camera and having been a Pentax user over the years I'm glad they are making a decent camera again, after the somewhat disappointing K-7.

I have incidentally bought more Pentax cameras than any other brand - here's the list:-

Pentax ME Super
Pentax 645
Pentax MZ-5 
Pentax MZ-50 

Pentax *istD
Pentax *istDL 
Pentax *istDS
Pentax K-10
Pentax K-7
Pentax K-5 ??????.............. Maybe.