Been a while since a first impression post. Enjoy.
Surprisingly instructions had some stats for the Imperial Knight.
One range weapon is Rapid-fire Battle Cannon.
My guess is R 72" S 8 Ap 3 Ordnance 1, Large Blast. Effectively it can shoot two large blast ordnance S 8 Ap 3 at 36" and cannot charge. Based on minibook 40k6 pg 138.
Other range weapon is Thermal Cannon is some sort of melta weapon that is not found in corebook. No idea. Please provide the trait. If you know the book and page I'd deeply appreciate you letting me know.
Honestly after seeing the traits in the instructions this 6" beast isn't as intimidating as I thought. This model can easily be introduced into standard 40k games. Of course the digital/hard codex can change all these things. Guess I'm terribly surprised that all traits except ranged weapon traits weren't provided. Almost as if half the model wasn't available for use. We'll find out when people start sharing the thermal cannon trait in the digital codex. Unless someone knows which dead tree form book its pulled from.