yeah XSL is a very nifty way to customize the appearance of your Bulletin Board.
Its like CSS for HTML. But a
lot advanced form of CSS
.
Theres one other thing about UBB vs OpenTopic. If you get lots of users, and are worried about band-width cost, I suggest you should go for OpenTopic, since it will provide the speed and the costwise solution. I mean you can't have UBB with a million members getting several lackhs post per day, and serving millions of page views. But with OpenTopic anything's possible.