BUT! There were a couple of things that everyone was in agreement with and I thought I'd toss them out. These were in the context of video games but I think they're going to apply to writing as well. At least I'm going to try to.
If there was one thing all the women on the panel agreed with was they wanted female characters they could relate to and male characters they could lust after. Part of this goes back to my post on creating sympathetic characters but let me dig in a little deeper. If your main character is a woman, she probably shouldn't be a stripper or a prostitute or (in their words) a guy with a pair of tits slapped on. They should be someone you'd like to be friends with. Witty, smart, a little self-doubting/insecure, but cool and confident. She should be competent at her chosen profession. She shouldn't be helpless or simply be the object of someone's quest. She can be captured but she needs to be trying to get her own ass out of trouble, even if she fails. She needs to be appropriate. Again, they want to see women in action/combat roles but they want to see explorations of what that means from a woman's POV, not as a male character with a woman's form superimposed.
Relationships are a big part of what seemed to be important. She needs to have friends of her own. She should have love interests and care about what happens to them. If someone's house gets blows up, they wanted to know if the people inside were all right, not if they'd lost all their stuff. (apparently a Fable 3 plot-fail) Relationships and the emotions that come from them were powerful motivations and hooks. Your female main characters should care about the people in their life and how they're doing, what they're doing.**
Several of them brought up Ripley from Aliens and how motherhood as a theme and a motivation to why Ripley needed to kick ass and get away really spoke to them...even to the women without kids. As they said, every woman has the potential to be a mother.
Surprisingly, most of the panel didn't have a problem with slutty characters* so long as the woman owned her sexuality. It was ok for girls to chase boys or dress revealingly (And with style. Accessories are important, it seems) but it was important that it be her choice. Its ok for her to 'get naked' but it was not ok if all her clothes were torn of by an explosion/melee attack/wild raccoon. Sexuality was ok, plot-dictated titillation wasn't, by and large.
Finally, this wasn't from the panel but from what my fellow writers have mentioned, let your female main character drive the action and not just be caught up in it or purely reacting to it.
That was about it, in the hour long panel they mostly talked about when it was alright to be slutty, characters they could identify with, and motherhood as a powerful motivation/theme. I have feeling this panel could have gone on much longer and it certainly is a topic for more
*though they didn't like overly-pretty characters. Apparently clear, smooth skin was a hot button for them. Who knew?
**This was partly my inference as they didn't come out and say this but they talked at length about their character's relationships with NPCs in their games. So this was my takeaway and it was a bit of an eye-opener. Guys don't generally care about what other people are doing, not in the same way. We'll ask 'how's it goin?' and that's good enough for us.