I'm terribly biased as it's my favourite ever show with my favourite character, but I'd say definitely yes. I'm probably going to set you up for sadness and maybe a little disappointment because I loved it so much I might be over selling it ;)
There are very few shows with such a wide array of interesting characters - different backgrounds and traits and almost all of them flawed to a greater or lesser degree.
Plenty of shows have great and strong characters and some shows have a lot of them, but for me Deadwood had more that I really cared about (as a viewer).
See, that's what I've been trying to figure out. The more I think about it, the more I want to just go ahead and watch it. I probably will eventually.