Yeah, always. If you don't think before you speak, what exactly are you going to say? I like to be constantly aware of the sounds I'm going to utter in front of people. After all, you never know when what you say is going to come back to haunt you. I don't, however, look blankly at someone for a minute while I try to phrase a response for whatever he said. At most, it'll take me five seconds to contemplate what to say.
I also normally think about what I'm going to type as well. I read over my post about three times as I make it; once to make sure it makes sense, once to pick out spelling and grammar mistakes and once to read it aloud to make sure it sounds okay. Reading over something three times normally tells me if I'm saying something I shouldn't be.