In reply to Ireddek: I have used Pentax K10D for long time. It is a great camera, very durable. It has different sensor and probably firmware too than K-r, so I can't tell anything about K-r. About K10D, the only annoying issue was high noise in ISO 400 and above. In my opinion, it was mostly a problem with firmware and denoising algorithm causing visible regular artefacts in high ISO. Here are my photos taken with K10D
http://www.flickr.com/photos/mloskot/tags/pentaxk10d
I have used fantastic old manual lens SMC P-A 50mm F/2.0
http://www.flickr.com/photos/mloskot/tags/smcpa50mmf20/
Summary, if you have Pentax K-mount compatible lenses, I would stick to Pentax body as old Pentax prime lenses are fantastic quality.
If you don't have anything now and investing in new kit from scratch, I think I would look for Canon or Nikon. I have just switched from Pentax K10D to Nikon D7000 but no I have to live for next months with kit lens only
You may find this helpful:
http://kmp.bdimitrov.de/