That whole trap door thing gave me the willies. It seems you have to stand with your heels hanging off the edge to get the trap door to close over your toes. The other thing that I would be worried about is how the ladder is right up against the tree. Normal ladder stands are tilted -- the way a ladder normally stand against a building.
Nope. This one is not for me. I'll take a more standard ladder design.
PS: I have a lot of advice from guys who have built raised box blinds. Their advice has been unanimous: forget trap doors and use a door on the side. It is not a good idea to build something that is a potential weak spot into the floor.