Yes, off topic forums are a vital part to the forum, especially if the board's theme is fairly serious, the off topic section is a good place to wind down after some serious discussion.
Yes, my forum has an off topic section. I guess it is important to be outside the webmaster discussion sometimes and participate in some general discussion.
Off topic sections are often overlooked, but they're also a very important part of any community. In fact, it's hard to establish a real sense of a community without one.
Yes. I think these are needed on every single forum as sometimes it's good to just hang out and chat with other members about whatever. Keeps posts coming to your forum too rather than them just talking elsewhere.
My forum does have off topics sections because I feel like that attracts more members. If the forum is focused on one thing that people aren't really interested in they won't stay for a long time so I make an off topic so they can chat about things that they are interested in too.