So, I just watched this film...
...And I must say it was shocking (mostly the eye-gouging scene), but not as bad as I thought it would be. (Isn't the anticipation aspect of gore films great? That's why I like them.) I consider myself a gore/sick film "novice" with titles such as these in my history: Audition (Unrated), Ichi the Killer (Unrated), Visitor Q (Unrated), Salò o le 120 giornate di Sodoma (Gaumont), and now this one. I've also seen stuff such as Evil Dead, Evil Dead 2, Dawn of the Dead (original), and so forth.
I thought the gore in this film was about 90% realistic. The chicken scene was so fake it was laughable. (If it weren't for the chicken scene, I'd say the gore looked about 97% realistic.) I can definitely see how Charlie Sheen thought it was real, especially if he watched it on VHS and it was grainier and harder to see the special effects.
I'm hesitant to watch films such as Men Behind the Sun and Cannibal Holocaust, though, since I heard that animals really died in the making of them (true?). I'm not a fan of real violence, as it were. I'm thinking of tracking down August Underground's Mordum since I hear it's the most (or one of the most) violent films ever, but again, the anticipation has me hesitant. Ha ha.
All-in-all, great [gore] film, and I recommend it.