I was actually disappointed with the heroic version of Kurns...with all the talk and wonder around Kurns Tower, I was hoping for it to be more in line with the Guks or a hair below Ferzhul in difficulty...and we breezed through it all within a half hour, as if it were an Obelisk of Ahkzul run instead. Kind of anti-climatic considering you needed an access quest to get in.
(Technically we spent 43 min in the instance, but that was because we were looking for the quest updates.)
I haven't gotten the joy of going into the x2 yet, but definitely looking forward to it, I hear it's pretty challenging. Though this just kind of points out how misleading the heroic Kurns is in this aspect as well.