I was there too. It's amazing how much more popular he is now than when I saw him 5 years ago, when only about 50 people showed up. But I knew it was going to be crowded last night. However, we arrived around 7 and got seats in the back. But we had seats! :)
My wife (who is 8 months pregnant) and I dragged her out-of-town friend with us, who has never read a GRRM book. She was a good sport, as we were at the Tattered Cover for over two hours, waiting for the man, listening to the man, and then waiting to get the man to sign our books. Well worth the wait. He was obviously tired when we got up to him, but still warm and jovial. My wife insisted we get a photo with him. She's a new fan (read all three books this year) and was quite excited to meet him.
I looked for Brotherhood tee shirts, but only saw a couple near the end when I was talking to a guy who just moved from Chicago. I guess that was you, nova, with the black tee and white logo who ran up to the line to talk to two gals wearing Valar Morgis (sp?) shirts. I almost stood up before George came out to yell, "Any of the Brotherhood here" but chickened out. I figured I would then spend 10 minutes trying to explain who I was, what my old forum name was and how to pronounce my new one.
Anyway. Let's if I can remember anything not already mentioned...
Clifford the Dog
In addition to the -4 people attending a signing in St. Louis, he told a couple of other funny stories from the same tour. One was a signing at a Barnes and Noble in Dallas (?). When he arrived, the parking lot was completely full, which made him very happy. However, there actually two signings that day. Him in the front, and the "junior member" of the bookstore dressed up as Clifford the Dog in the back with a rubber stamp for a paw to sign books for the kiddies. Clifford = 100's. GRRM = 2. :) Then he said it was very hard not to dance around the stage and say, "I'm number 1" (New York Best Seller List) and that he was ready to take Clifford on.
The Finger
For some reason, my favorite joke was near the beginning, when he mentioned (like nova said) his arm was about to get gangrene and fall off from signing so many books. That would be most unfortunate, because he writes all his books with --holds up his right index finger-- this finger. It gave me a funny image of him hunched over a type writer pecking a 1500 page manuscript with a single finger.
Boba Fett
He talked about the Boba Fett syndrom. It is basically how a side non-character captures the imagination of the reader/viewer way beyond the creator's intent. It's the "cool" characters that have one line or five minutes of screen/page time that gather a cult following. He also said he gets fan letters where people say, "I love Tytos Blackwood. Can we learn more about him?" He called Oberyn Martell one of his Boba Fett characters.
He also told a Boba Fett story about his Wild Card series, but it contains spoilers. I can tell it if you all want.
Tear out the Pages
He encourages all his readers who want a complete map of his world to tear out the pages and assemble the entire map. That way you can buy more books. :) He did say a map of the free cities would be in aDwD. You all probably know that, but I didn't.
The Moving Carrot
Someone brought up the the book Dance with Dragons has been the "promised next book" for a long time. First as the end of the trilogy *cough cough*, then as book four, and now as book five. Martin says DwD is his moving carrot, dangling from a string in front of him. The book he can never reach. He wants to get there fast, though, since he doesn't want someone to steal his title. To probably repeat what others have said, he has 500 pages done with DwD, with another 500-600 pages to go. He hopes to be back in Denver next fall.
As an aspiring writer, it was both comforting and encouraging to hear his stories about "failed" signings and trepidation as he relaunched his career post-Hollywood. He also mentioned how it wasn't the advertising budget that made him a success now, but the book sellers and fans recommending the book. Well done, guys. :) Like I said earlier, the effort of the fans was very obvious in Denver. Turnout increased 50 --> 350 with a single book. Not bad. Yes, it was five years, but still only a single book. ;)