Our first meeting is March 14, so same week as yours!
They didn't say anything in particular about the benefits of the program (statistically, I mean...they just talked about obvious things like how you'd meet other people and how someone might bring up something that you hadn't thought about, etc.). But yes, they said the same thing about how the pilot program was done at Yale. I'm excited too because apparently there's a pediatrician in my area who's considering this same concept for well-baby care, which I think sounds great (especially if I end up having a good experience with the prenatal group).
From what I got, partners were "welcome" but not especially encouraged or discouraged. I do know what you mean about wondering how you'd be with other people's partners, but I'm thinking that if the partner really wants to come to the group thing, then they must be into the whole idea, and would be pretty open to whatever I have to say. But then, I am not at all shy or reserved, so I honestly hadn't even thought about that!
And, from what my midwives said, it will definitely be a mix of first timers and other women who already have kids. In fact, that was sort of touted as a benefit to me: know you're not alone, and also benefit from the wisdom of women who've done this before.