I've been very pleased with my K5, taking it on backpacks and treks where I simply didn't want to carry the weight of my 645D and associated lenses. Still, IQ wise, there is really no comparison between the two but the K5 does very well with night sky/nightscape work. Hence, my dilema of upgrading to the IIs or not. I went to
Digital Photography Review and
Digital Cameras, Digital Camera Reviews - The Imaging Resource! and downloaded the RAW files from the K5, K5IIs along with the same image files from the Canon 6D and Nikon D600. Although there were a few sections of the image where mild moire was introduced with the IIs, surprisingly, there were hints of moire in the same sections of the files of the other cameras, as well. Essentially, the moire issue, in my opinion, is a total non-issue for landscape/nature shooting...wedding dresses might be another problem. The surprising thing I found was how closely the IQ of the IIs held up against the Canon and Nikon, even when upresed to the same pixel width as the native files from the 6D and D600, particularly when comparing the detail of the threads/fabric weave on the DPReview studio scene. Carrying the scenario another step, I upsized the Pentax, Nikon and Canon files to create a 30x40 inch image. Even at that size the IIs image, compared well, if not perfectly, against the Nikon/Canon files. On canvas (most of my printing) at a normal viewing distance the typical person would not be able to tell the difference.
My K5 will be for sale and the IIs will be my new upgraded backup.