ODST was the meal. Firefight was the dessert, and made the whole thing so much better. So many hours spent on this in single player and co-op, and so much fun had. It's genuinely one of the best experiences I've ever had with Halo.
I hope they don't make it as customizable as Reach firefight. I can't remember what the issue was, but I felt like Reach Firefight wasn't nearly as fun, due to being able to make it too easy on yourself or something? I think ODST FF felt like more of a set challenge to overcome and score par achievements on.
Not sure why it's lagging behind, but I'm really glad it's here now.