Okay, I actually went to three things at Readercon; this was the last. As it was a discussion, I didn't take many notes; and since work is going fairly well, I think I can spare a few minutes to type up my few notes while they're fresh (and while I'm waiting for the Advil to kick in. Boo, headaches.).
Short non-spoilered version: There were only six people in the audience, and one of them, well, I had to say at one point, "Excuse me, I wasn't finished talking." Despite, or because of, that John Langan did a nice job as moderator. No-one really had answers for my questions, but a few interesting points were brought up for me to ponder in other areas.
Here's the spoiler version. If you haven't read the books, it won't make any sense; and if you might read the books, it will ruin things for you.
( SPOILERS for the ending of the Dark Tower series )
Oh, and hey, I got thanked in the program for the suggestion of this discussion! I am unreasonably chuffed by this.