Considering a switch to Pentax from Nikon

I did exactly the same thing as you. Moved from a Nikon D7000 to a K5 because of the limited primes. I can tell you that I have never been happier. I encountered some focus issues in extreme low lights (dark indoor restaurants). For normal day to day shooting it has not been an issue.

If I were you, I'd wait for the K5 II.

Some images with the K5 (the latest seventy or so):
http://www.flickr.com/photos/sanjeev_das/