SPOILERS AHEAD!
It was pretty terrible. I didn't like it very much. I went into it not expecting much and thats what I got.
As you may or may not know, I love watching movies and reading books which offend people and are generally disgusting or disturbing. So I really respect them for pushing the envelope a little bit. They went further than a lot of hollywood movies go, especially since this is just a summer movie. They weren't afraid to get a little weird.
However, the weird rape scene was not well executed in my opinion. It was not particularly disturbing to me, even though it was technically bestiality. It was just uncomfortable, I did not care. This goes for the other weird sex scene. It was just awkward for everyone. Nobody was particularly disgusted/turned on. It won't make the most disturbing films list(s) (yes, there are many. Yes, I strive to watch them all).
I think this movie would have been better if they went a little deeper into the ethics. They made the Dren character quite unlikeable so the whole human side to her kind of got thrown in the trash. Even though she appeared to be more intelligent than most humans they kind of made her a 100% instinct monster at the end. At least they made the girl smarter than the boy version... cause I'm about to have a feminist rant in the next paragraph.
They used the old : "Don't listen to the bitch". What I mean is that basically whatever the female lead character did was the opposite thing that most normal people would do. Like keep the f***ing mutant animal-human child. I guess screenwriters think all women have some sort of overwhelming maternal instinct that would convince us to do stupid shit especially for anything carrying our genes. Hell Nawww. Should have listened to Adrian Brody when he wanted to stab the thing. Then at the end... oh gawd why.
So I guess they were going for a kind of Freudian feel with this one. With the whole daughter having sex with the father and then turning on the mother and then the opposite when she became a dude. But it really didn't work according to me.
So, thats my opinion on Splice. Don't watch unless you are really bored.