I think I'll go with "Monthly". Once in a while we get some heated discussions, considering how things go around here, but that one that f0dder linked is the only one I saw mouser closed for going too far.
Examples of somewhat rude threads would be the one that Darwin mentions, that other one that was spawned in the Opera 9.5 thread, with zealotry accusations and everything, and the one about the Mac, hehe, that one was quite the show. In every other forum, people would be trolling in those threads, derailing then to the point of making the original topic or question irrelevant.
Like, for example, if someone asked about an antivirus, people started to recommend switching to the Mac or Linux. Or complaining about an app they never tried. But those are the less rude situations.
Then again, like everyone says, this is a very nice place, considering some of the other forums I hang around, one being really mean sometimes. I have to say that is mostly frequented by teenagers, and their "Living Room" is particularly hilarious, because of the naiveness of some people. Anyway, people is always meaner in the Internet than in real life.