I am now 1 round into my first game of Heroes of Terrinoth on the Heroes of Terrinoth Gamemat. I must say I'm a little disappointed. The mat is cool, for sure, but it's cramped, even playing with only two heroes. I think this gamemat is idea for a single player controlling two heroes. Any more than that and you just can't fit all the cards on the mat. It's not a problem if you have a nice game table with a cushion top, but if you're playing on a standard dining room table, it is frustrating to have some cards on the mat and some off the mat.
Since I don't have a nice table, I think I'm going to have to put my Star Wars Bespin mat underneath my Heroes of Terrinoth mat so I have more room. I really wish this mat were larger.