In trying to describe Deadwood to Brett, I found myself using the phrase, "The Western that Shakespeare would have written, although with a lot more 'f*ck's and 'c*cks*ck*rs.'" Watching tonight's episode (which is on as I type this) only reinforces that description. David Milch and his writing staff have created an artificial, almost poetic dialogue style that seems quite unlike anything ever heard in a Western before now--and, I'm quite sure, quite unlike anything ever heard in the Old West, either. (One thing I can say for sure is that the Old West never heard the word 'f*ck' used so so freely and in so many grammatical forms. While the word itself, used to describe the sexual act, existed long before the era of Deadwood, its use as an adjective, an adverb, and pretty much any other grammatical form that Milch & Co. can shoehorn it into is a uniquely 20th Century linguistic device.)
The story of Deadwood, heavily drawn from history (gee, just like Shakespeare's plays!), is constructed around the transition of a lawless region to a territory and then a state. Its characters are richly rendered from history, given personalities (some none too likeable), but its plot seems to stick close to the plotted course of the past. But it's not the story that makes this series so memorable--it's the distinctive voice that Milch has given it. No show has dialogue so convoluted, so complicated, so sometimes enigmatic. It evokes the era without ever accurately recreating the era, if that makes any sense. (If you'd like to learn more about how it does and doesn't follow real history, this is a very good site for such information--and it's fascinating reading.)
Ian McShane's performance as Al Swearengen is as irresistibly watchable as a high-speed nine-car pile-up; you don't necessarily like what you're seeing, but you just can't look away while it unfolds before your eyes. For my money, though, the best actors in the series are Timothy Olyphant, who plays Seth Bullock in an intensely understated manner; and Robin Weigert, whose take on Calamity Jane is rambunctious, unrestrained, often undignified, and yet noble in its own warped way. Neither gets to chew the scenery the way that McShane does, but they're quite successful in stopping him from stealing the show.
Can't say you'll like Deadwood if you like traditional Westerns, because it most definitely isn't one. As for what it is... well, I'll get back to you on that...