I'm currently 7 episodes (of 10) into this show. And I can say it is pure AWESOME!! Love it!
How popular or well known is it in the US? As the only reason I've even heard of it is because I saw this thread a few months ago. It's shown on Sky Atlantic here in the UK, but I missed the first few eps so didn't catch, and plus I barely saw it advertised anywhere. Anyway I randomly watched the first episode online a couple of days ago, and since then have been using all my free time to watch the others. Ep 6 with the albino, haha jesus christ.
It's easily become my new favourite show, sorry Game of Thrones. Definitely recommending this to everyone I know.