I truly think that is a killer feature
Having a couple big boards myself, I quickly found that my choices were
1) Gettings faster, better hardware
2) Pruning the database out of old posts and threads
Although InnoDB is a little better about locking, I can truly say that MySQL starts choking whenever I reach the 1M posts goal. It just does not like it. Then you start dealing with server optimization, replication, and improving the hardware. All of that costs money.
A good solution for me was moving all the threads and post to a "secondary" table. By doing this, I operate with light tables, while keeping all the content in secondary low-hit tables. This saved me a bunch of grief on the MySQL side. I was today really excited when I read that, something I have been doing for years out of necessity is now a core feature in some forum platform. Finally.