The ones I'd sent out last night before they were closed off were still valid. Perhaps you're just seeing the people who had invites but hadn't signed up yet?

It's growing on me. I've been surprised that Google, of all companies, has a product that's more attractive than Facebook. They're not known for their design, but I'm kind of appreciating the look. They seem to be coordinating it with a redesign of their other apps too, though GMail still looks the same for now... *edit* and there we go */edit*