Yes, it's all been done before, and better. It reminded me of several 'Star Trek' episodes too. Until recently 'Stargate: Atlantis' seemed to have found some originality, but I wonder if they are finally loosing their touch.
The 'Forbidden Planet' Id monster was never explained either. Why was it necessary for Sheppard come before they were able to confront it, if they knew all along what it was?
And if the time was 250x faster and they stuck that tree branch through the portal for 20 seconds, then it was sticking in there for 1 and a half hours. How come Sheppard didn't see it when he was waiting for a sign that they hadn't given up on him?