The last couple of episodes of series 1 were indeed, as you said, very brutal, and very hard to watch. But very well acted by all concerned I thought.
I watched series 2 on Amazon Prime last year, when I had a 30 day free trial. Am now considering subscribing to Prime, briefly, so I can see the third series :)
Have you read the books murraymints? I read somewhere that Diana Gabaldon, the author, held out from selling the rights until she was assured that they wouldn't alter her writing too much and from what I've seen so far it was a good move.