I'm doing this one first because I took minimal notes and it's currently winning the poll.
Description:
Was Ford sometimes too smart for our own good? Must you know who Earl Rivers was to appreciate The Dragon Waiting as one of our finest alternative history fantasies? Is Growing Up Weightless simply a great Heinlein juvenile? Did the Klingons ever have a truer friend? Did anyone write anything about 9/11 better than the poem "110 Stories?"
Chip Hitchcock, Patrick Nielsen Hayden, Teresa Nielsen Hayden
Again, this not a transcript, just notes on things that struck me (but if it's in quotes, it's verbatim). I'm using "JMF" as a blanket appellation, whereas various people actually said "Mike" or "Ford" or whatever, according to their personal etiquette of names.
I think the two themes of my notes were structure and exposition, and accordingly I'm going to rearrange chronology to give a more coherent report.
Structure (with a slide into theme)
Hitchcock: many of JMF's short works play with structure almost ostentatiously (that may be my word). They could feel gimmick-y but they don't. He cited the sonnet "Janus," which can be read at Cafepress on a poster (and other things).
TNH: JMF had a really deep understanding of structure. She thought it came via theater: "theater people understand the difference between the story and what's going on."
Later on, I asked whether the novels were playing off of established structures. (I always think of obvious structure as being a characteristic of the shorter works, but I could just being failing to recognize the structure of the novels.) TNH: it wouldn't surprise her, and someday someone will get a dissertation out of it. Two examples: (1) JMF had said that the plot of a farce depended on keeping apart, for as long as possible, two people who must not meet (getting tension out of the near-misses) and then bringing them together at the worst possible moment. This applies to How Much for Just the Planet? and (I think) Casting Fortune (I haven't read either yet). (2) There are echoes all over The Last Hot Time.
Discussion of Growing Up Weightless's structure focused on how it is almost one long tracking shot; see 
drcpunk's report for more detail.
Hitchcock: he helped arrange From the End of the Twentieth Century (booklog), and they had to work to space out the "agony stories," especially from earlier in JMF's career, where people try — reach out — and, mostly, miss each other. This prompted a very brief excursion into criticism-by-biography that petered out in either lack of knowledge or exercise of discretion, which was just fine by me.
Another theme: Hitchcock said that at the 1999 World Fantasy Con, JMF was interviewed by being asked to tell them about voyages. It was apparently very characteristic, and is not online "yet."
Exposition
JMF to TNH, during the editing process (I think): "I have a horror of being obvious." An audience member id'ed this as a paraphrase of Lord Peter Wimsey (to Bunter, regarding Harriet Vane), but it's not clear whether that was an intentional reference, and anyway it seemed to have wider application than Wimsey's comment (though, I suppose, Wimsey's could also be wider than regarding Harriet Vane).
TNH: one of the purposes of superfluous exposition is to reassure people that they don't need to know more: "Erase/Record/Play" is an example of the inverse. She found it difficult on the first reading (first few readings?) to figure out the backstory. Someone else in the audience said they thought they understood it, and now they weren't sure—I interjected that no, they should keep their certainty, the purpose of the panel was not to make people feel intellectually inadequate! [*] My opinion of "Erase/Record/Play", as I said then, is that if backstory was missing, that was the point (though I didn't feel I was missing anything that kept me from appreciating the story). TNH said that JMF's works drove copyeditors crazy because they need to understand things up-front, and she had likely read the story partly with a copyeditor's eye.
[*] I was reacting a bit crankily to some of Hitchcock's comments, because one of my pet peeves is any hint of false humility in asserting how difficult and deep one found a work. I freely admit that I may have been misinterpreting the subtleties of his tone, especially since I had previously perceived him as patronizing in a conversation. Also, I think my interjection cut off the original audience member from saying what they understood "Erase/Record/Play" to be about, for which I apologize.
On the other hand, TNH said that editing The Last Hot Time (booklog) was a constant exercise in genuine humility, having to go back to JMF and say, "I'm sorry, I just don't understand this," whereupon he would put in more exposition. The work was apparently originally novella-length, and while it's not a very long novel, I gather it was expanded considerably in the editing process.
(There's an interview with JMF on the Well that was cited as explaining more about The Last Hot Time, which I haven't had time to read yet. At the panel, there was confirmation that the book started out in Terri Windling's Bordertown shared universe, but moved out of it because it's not YA and then became more Chicago-y.)
Growing Up Weightless was also mentioned with regard to exposition, as an example of scanting obvious exposition but nevertheless telling readers just what they need to know, even if they don't know how they know it—specifically mentioned was the scarcity of water on the moon. Hitchcock (I think) answered the panel description's question with a "no," at least to the extent that the question was dismissive of YAs: the parallel adult plot is critical. I'm not sure whether this was directed at moving the book out of YA by the quality of the work or by its subject matter, but it was certainly discussed as exposition that didn't hit one over the head.
Another panel description question, The Dragon Waiting and Earl Rivers: PNH thought that when the book got to the Shakespearan stuff, it went into JMF's characteristic failure mode of insufficient exposition. I disagreed somewhat; I understood the events (unlike those at the inn), but I didn't understand their weight before reading The Daughter of Time (which sets out the myth and (one version of) the history of Richard III), because I didn't know what the book was playing against.
elisem said that JMF most often wrote to amuse Pamela Dean and the Nielsen Haydens, if one wanted help or clues for decoding references. Also, the three authors it most helps to have read are Christopher Fry, W.H. Auden, and Tom Stoppard.
Someone, I forget who, wants annotated works. Someone else: and all of the footnotes should start with JMF's characteristic "You must understand that" (in the "As you know Bob" sense, not in a peremptory sense). There was also a description of the famous footnote panel at Minicon, where various people just talked and the audience was given pieces of paper with * on them, to hold up whenever they wanted a reference explained. Apparently two unforeseen results were: (1) people using the footnote signs for the rest of the con, and (2) the custom being exported to Usenet, in the form of quoting bits of posts and appending just [*]. (I do it myself.)
Miscellaneous
Someone, possibly TNH: JMF's works were so often transformational, citing The Yellow Clearance Black Box Blues (an RPG adventure), and The Final Reflection, the foundation for all subsequent Star Trek images of Klingons. I would add How Much for Just the Planet? and "Winter Solstice, Camelot Station," both of which are widely thought to have caused a rewriting of the rules so no-one else could write that kind of Star Trek book / win a World Fantasy Award with a poem again. I have suspicions about The Dragon Waiting but I don't know enough genre-history to be sure.
Several someones: there is a lot of JMF in Paarfi, the narrator of Steven Brust's Dumas pastiches (booklog). I have to say this wouldn't have occured to me, but now I will have to look.
Elise: the stage manager in Planet? is the one character JMF clearly was.
Two stories from TNH:
- In a car with a couple other people, JMF apparently asleep in the back, a passenger said to her that "polish" is the only English word that changes pronunciation depending on its capitalization. A little voice from the back instantly said, "tangier." Her passenger turned to her and said something like, he hadn't believed the stories. TNH: they're all true.
- JMF was visiting New York and feeling somewhat unwell, so she suggested he sit at her desk for an hour or so while she was away. She had a printout of a symbol font tacked up for reference; and when she came back, JMF had quietly translated the whole thing as though it were a foreign language (the result is known now as "The Rosetta Roseannadetta Stone," and was one of the auction items).
And a story from Elise which seems a fitting conclusion: in an interview, she asked him a question that had been originally proposed for a panel and then shelved because it was too heavy: "I'm going to die, tell me a story." His emotional response: "No. You tell me a story, and I'll tell it after you're gone."