There was a sequel to the original, and then there was a remake and a sequel done more recently. I'm not sure if this one was a direct follow-up to the remake, or to the sequel, but it was the same actress. It was brilliant, as I said - just VERY brutal. However, it was in some ways less exploitative than the 1977 version. Frankly, that one went out of its way to show the girls nude whenever possible, so that you almost felt like a participant in the rape scenes. This one doesn't once try to be titillating - nudity is very sparse, and when it does occur, it's about as UN-titillating as you can get.
The 1977 one must have the longest rape scene in movie history. It has to be, what, 45 minutes of the film, if you count it as a continuous moment? Just rape after rape after anal rape after rape.
I don't really know what to think of the original. It seems pointlessly repugnant and awful and even poorly made at points (the boat scenes, the audio), then other times well acted and horrifying (the bathtub scene is extremely effective, and the rape scenes are effectively horrifying even if extremely long for no real purpose). People complain about modern "torture porn", but I Spit On Your Grave 1977 was way, way worse in terms of what people complain about than the handful of modern ones I've seen (Hostel, Saw III, etc). For that matter, so is Last House on the Left. There's a major difference between having someone torn up by some ridiculous machine for a couple minutes than a half hour of psychological and physical torture, humiliation, and rape by relatively realistic low life scumbags.
I haven't seen the new ones, but I'd be surprised if they're as brutal. What do you think Indy?
These films all do come across as kind of gross in the titillation factor, at least in their marketing - look at the posters for all 4 films. I guess I can't blame them for doing this either, as the fact they've made 4 of these films now indicates they're making money.
**SPOILER FOR IRREVERSIBLE**
As an aside, the plot description of part 3... Just once I want to see a vigilante movie like this where they torture/murder the people, and they totally have the wrong people. I mean it in one of these low budget shocker flicks, not something like Irreversible. Probably beyond the scope of what the writers of these sorts of films are going for though.