In an interview at TERAfans, Dog speaks to the leveling curve, the PvP, and the ease of the overall experience. He also admits to putting in "42 hours or so at the beginning before I have to sleep or before my guild forces me to sleep."
So how about that endgame? The interview states that he hasn't seen much of it as of yet and offers no insight into TERA's super secret political system. Dog does indicate that he ran every dungeon in the game at least once during his whirlwind leveling journey and is "a little worried about how easy they are." We'll add the usual this-is-the-Korean-client qualifier here, and we'll also direct you to TERAfans for the full interview.