It's definitely a hard watch.. But if you like gore horror then it's amazing at that, but then again not worth watching if you're not into it or you think it can be to extreme for you.
Sometime is kinda hard to separate certain movies between Horror gore and "Torture P#rn". Titles like "Human Centipede" are in my opinion just plain Torture P#rn, with nothing to offer except inhuman torture scenes. Martyrs seems kinda like that too.