I'm totally reviving an old thread here, but I've just started watching Deadwood over the summer. It's pretty awesome, and the characters just keep getting more interesting as the season has come along. Along with the obvious heavyweights like Olyphant and McShane, Powers Boothe is just chilling as the evil Tolliver. There are so many interesting character actors in here - William Sanderson, Jim Beaver, John Hawkes, Titus Welliver - and that's just a small portion of them. I also think Molly Parker, Paula Malcolmson, and Robin Weigert are great in very different roles.
I've been writing about Deadwood each week on my blog if you're interested. I just wrote about episode seven this week. Here's a link to all of the posts so far:
http://www.ptsnob.com/search/label/DeadwoodI can't wait to finish out the season and keep rolling through the show.