I once had a friend who got really worried when I invited him to come to a LW meetup with me, and later found out he had another friend who'd read this site and then decided that everyone else needed to be more rational to make her own life easier. The worst I've encountered in meatspace personally was being asked why I believe what I believe a whole lot (which can be really useful when you're actually deciding something, but being asked to cite your sources in conversation also really interrupts the flow of things), which was more than balanced out by the good conversations. So my general impression is that LW as a high standard deviation in acquaintance/conversationalist quality, and either there's more good than bad or I've had good luck.