I agree completely with what AJ and Rory have said. What we've got is a bunch of people that share many common interests coming together and saying "Wow, look at all these new questions to answer!" - and that's precisely what folks have been doing for the most part.
Meta involvement has really picked up, we're having the kinds of conversations that we need to be having and I think, with very few exceptions, this went off without irritating anyone too badly. Things have rapidly come together and an even better site is emerging, which stands a shot at being one of (if not the) friendliest and relaxed places on our network while maintaining the high signal to noise ratio that our brand promises. I think this is rapidly becoming a site that other sites can learn from.
On the technical side, we learned some stuff. The first wave of migrations didn't go as well as I hoped, a couple dozen questions that should have stayed on video were accidentally sent over. However, we refined some queries, improved some tools and subsequent moves went much, much better. Folks on Video that were equally into sound are understandably a little bummed about seeing their rep now split between two sites, but quite a few seem to be digging in and having a pretty good time here.
The actual re-branding of Video went extremely well, with almost no snags at all (save for a few minor text corrections). We were hoping that the split wouldn't cost Video too much as far as participation and traffic goes, but it actually appears that they're now doing better than they were before we started 1. It'll be a few months before we can say for sure, but I think this split was needed, and long overdue.
All in all, I feel as if the project was a great success, and those that actively helped to move things along are directly to thank for that. We (Stack Exchange) are still not yet done, we're looking at places where we can target certain kinds of ads very likely to bring in new and knowledgeable contributors, for both sites. I'll have more on that in separate meta posts on both sites, but we're really excited to see how well things turned out.
Good job, everyone! :)
1Analytics reset when we changed the domain, I don't have hard numbers ready, but will in the somewhat near future. This will also make Area 51 stats seem strange, or scary, pay no attention to that for now. (I'm going by memory of averages prior to starting)