I'm 5'11", 260lbs and purchased Kona's Hoss in mid October. Since then, I've been riding almost daily - mostly trails but also bike paths and roads - all I can say is Kona has made a hell of a great bike!
I've had nothing more than some minor break-in issues (front derailleur adjustment, brake squeal, etc.) and the bike feels extremely solid. I did switch out the original stem to better suit my riding style; and my Hoss - for some reason - came without the (Shimano M505) clipless pedals listed on Kona's spec page. (I'm trying to get an answer from Kona on this, BTW - will let you know what they say).
Anyway, it's a truly great bike for big folks who want to enjoy riding trails without fear of the bike beneath them falling into pieces...