Several months ago we considered switching the board to WWWThreads (the name of UBBThreads before UBB bought it). It seemed promising because of the additional features and the fact that it used MySQL -- a product that we like a lot.
We purchased a license for the board, ported the data from from UBB, and started experimenting. It was horrible. Tim (our main programmer) and I were fixing errors in the code before we could even install the database -- keep in mind that this was a professional product that was not cheap, and we were having to fix bugs in the code just to get it installed!?
Finally the software was installed, and the threads from flyertalk were moved in to the MySQL database.
The performance of the board was slow -- very slow. Imagine the slowest day that you've ever seen FlyerTalk and double it. That was WWWThreads.
I think that we'll stay away from them -- we're still open to changing the backend of the board, but it won't be to Threads.