I thought it was a good film, but not neccessarily a film that i'd recommend to people to watch. It does actually have a decent story to it and it's definitely not the "gorno" that it's probably being painted as (although it does have a lot of sex and gore, but it's portrayed in a different way to films like 'Hostel'). The last 45 minutes or so is some of the most horrible stuff committed to celuloid, and you definitely need a strong stomach to watch it all, but it does have a point.
JCR is right though, it shouldn't be watched for "entertainment", the violence isn't 'Saw' or 'Final Destination' style OTT that you can laugh at, its realistic and nasty. I'm not at all surprised that the BBFC took exception to the film as it is a very adult film that should only be watched by adults with a sound mind, it's just annoying that everywhere else in the world adults are allowed to see it while the UK's adults are treated like children...
The 'Disturbing Movies' thread in this forum has other opinions on the film if you're interested in what other people thought of it.