British Journal of Photography has a 4 page review of the K-1 this month (7853 Nov 2016) - the BJP, if you don't know, is the oldest (since 1854) and one of the most respected photography journals, so it's a bit of a coup for Pentax. If you're interested in art photography, I'd highly recommend a subscription.
It is a well-informed and very favourable review. They pick up all of its strong points (including knowledgeable and thorough explanations of pixel shift, K-mount compatibility, and the sensor itself) and only really pick on its slower burst rate and limited flash system compatibility, as being barriers to professional uptake.
The headline from the feature reads:
Quote: It's a hefty beast of a camera that wipes the floor with most DSLRs...
...Photographers who have not spent time with the K-1 will have no idea what they are missing. Ignorance is not bliss.