HoBykoYan,
I have been shooting mainly in TAv mode which allows shutter speed adjustment on front edial and aperture adjustment on the rear edial. I have ISO set to automatic in a range 100-6400. Apart from the IQ of the K-5 the ISO flexibility is where it really is ahead of the K-7.
I have found shooting like this with a good ISO range provides a great deal of flexibility, and the K-5 images are still pretty good at ISO 6400. If you are into low light photography then the K-5 is going to spoil you.
The only issue you are going to have is the on-going desire for fast glass, and that costs plenty
.
I have completed some landscape photography this weekend using the DA 21/3.2 Limited and was really happy with how this lens draws, the colors, and the sharpness of the images. Pretty good really - there are a couple of examples I have put up in my albums.
Enjoy your photography - that is the main thing.
Ross