There is an interesting discussion of early modern coffeehouses at "Crooked Timber." I couldn't help but think of Berkeley's Alciphron, or the Minute Philosopher. The four main characters of the dialogue are Euphranor, Crito, Alciphron, and Lysicles. Alciphron and Lysicles, the freethinkers or 'strongheads' (whence Alciphron derives his name), are champions of a certain sort of coffeehouse philosophy; they advocate it, and the freethinking it involves, as the wave of the future. The two are very different; Alciphron loftily insists that atheists are more moral than Christians, while Lysicles, the hotheaded hedonist, argues that morals are for stupid people, and that it's obvious that we are all economically benefitted by vice. Throughout the work Berkeley satirizes the freethinking of the coffeehouses (with which he was very familiar from his London days with Richard Steele and Jonathan Swift), which he prefers to call 'minute philosophy'. Lysicles continually makes outrageous claims he can't defend rationally (and when called on it, insists that he doesn't have to defend them rationally); Alciphron, much more sober and philosophical in nature, is given to rather funny rhetorical outbursts in which his rhetoric overtakes his reasoning (they often begin with apostrophes like, 'O Justice! O Truth!'). Euphranor and Crito, in a sign of the excellence of Berkeley's literary skills, have very different personalities despite defending the same side -- Euphranor is consistently the simple, self-taught Platonist coming into his first contact with these odd but interesting 'strongheads', while Crito has dealt with their kind time and again, to the point of exasperation, and is always more cynical and mocking in his assessment of them. Throughout the dialogue, of course, the minute philosophers are outmaneuvered by Euphranor and Crito, in part because the latter see right through the coffeehouse tactic that Berkeley mocks most mercilessly: the freethinkers advocate freethinking almost entirely by demanding, without argument, that you only think one way (their way, of course).
But it's also worth noting that Berkeley's mockery of coffeehouse philosophy is based on his own experience; he heard the coffeehouse freethinkers himself, and it was this that convinced him that their written works hid a more anarchic and destructive agenda that needed to be fought. It's not that he despises coffeehouses, or even coffeehouse discussion; it's that he thinks there is a trend in which people are pontificating on matters that they've never taken the time to research or think about carefully -- the ultimate temptation of coffeehouse discourse. As a result there's a lot of quibbling over minute details, a lot of rhetorical bombast posing as argument, and more concern for being clever than for finding the truth. It's this that he can't stand about the minute philosophy he found among the coffeehouse crowd. So we should perhaps avoid taking an either/or position here. It's not that coffeehouses were wondrous marvels of sophisticated rational discourse; nor is it that they were simply useless gossip mills filled with vulgarity and bombastic punditry. Here, as always, the danger is in not trying to find the happy medium.