No, I haven't seen "The Man Behind the Curtain" yet, but I did read the synopsis of the episode at MSNBC and Wikipedia. (I know. It's pathetic, really, that I can't wait a few hours to watch it for myself - I have to find out what happened.) I also went to here for the pictures of the real man behind the curtain.
If you haven't watched it yet and don't know what happened, please stop reading now. As they say, here come the spoilers. *******
Come now. Do you truly believe this is the end of John Locke? He is probably the most pivotal character to the show. He was the original man of faith on the island, even before Eko came along. He really isn't going to be relegated to the Lostaway graveyard, like Boone, Shannon, Ana Lucia, and Libby, is he? The island has such a hold on him, both mentally and physically - it has seemingly given him the power to walk again. Why on earth would we think this is the end of him?
Ben shooting Locke? No shock here if you've been paying attention to how the series has been unfolding and how this particular episode was presenting. Locke challenged Ben. Ben doesn't like his authority threatened, so he'll do what he thinks is necessary to maintain it.
As for Ben, I have to say I'm befuddled as to what his plan is now. We now know why he was so adament that Locke kill his father - Ben had done that very deed himself. And, surely he couldn't have been so suprised that Locke would have filched the tape recorder. One thing we can say about him is that he isn't crazy in the conventional word. How else to explain all the happenings in the room when Locke turned on his flashlight, and that mysterious appearance of Jacob?
Gael Fashingbauer Cooper has thoughts similar to mine.
Update: I've seen it. I was totally creeped out by Jacob's voice.