So far, the response has been fairly good, though of course we have the usual complaints that always accompany change. The feature set is definitely not complete at this point, but apparently future speculation is a definite no-no under SEC quiet period rules, so you'll just have to speculate yourselves.
The launch itself was kind of weird, given the labs nature of the launch, and the fact that it coincided with the Image Ads announcement, and came on the heels of the new Blogger redesign. We got some hype right away over our support of ATOM feeds, but its not like Mark is a disinterested party.
Of course, there were some, um, "easter eggs" (yeah, that's it) in the product. My email address was the bounce address for the first couple of days for invites, for instance, and Dave's address is still hard coded in the promotion boxes (that'll be fixed soon, honest). The bug list is getting shorter though, honest.
Some might note the similarities between Groups2 and Archive, a technology demo we did over at Neotonic.
Lastly, I'd like to put a shout out to my friends still laboring on Y!Groups. It may look like nothing much has happened with it, but still working despite the growth is a testament to their prowess.
So, hopefully you'll like some of the new features and things we've attempted with Groups2. I like the one about the "cross between a blog and Usenet" myself, though all the "portal wars" talk seems silly to me.