I see what you're talking about, but could be anything, given that YouTube has compressed the vid, etc. I've not seen any tests of the DA18-135 exhibiting massive purple casting either, and that wasn't a particularly contrasty scene, but I'll look for similar examples in my shots and on forums. The sensor and the camera's image processing seem great to me so far.
I remember paying over $1600 for a K20, lol. A good friend has a D7100, which I have ogled and played with- super nice, and I was appropriately envious. Of course I've had Pentax gear for decades, but I'm not crazy biased- just always considered Pentax more of a true enthusiast brand rather than a workhorse. I like this K-3 better. I think the ergos are nicer and the menus are more intuitive, and the fact that great legacy lenses all function and are stabilized is worth something. It will be interesting to see a comparison review.