Why did we switch away from phpBB. I've managed it before and liked it. But SQL is much better I'll admit.
Because SMF is much better

phpBB was over five years old and required mods to get any features, and you had to spend a lot of time figuring them out to get them to work, much less work with other mods in place. This forum is much newer and all these features are built in, ie I didn't need to mod them in.
There are lots of other cool features, like the cookie tracking working properly so your unread posts stay unread when you log out, and logging in doesn't become a burden on some people who don't log in regularly.
Also, for anyone else who hasn't seen it, Mustash has started this thread where people are discovering the various new features of this board:
http://www.kumoricon.org/forums/index.php?topic=4770.0