There is quite a bit to say about this movie, but a lot of it is only to be said to someone else whose seen it, so I'll keep it short. It's up to you to decide anyways.
I went into this movie expecting what my friends said to be an extremely depressing and bleak outlook on relationships. I didn't really get that out of it, well, I got the bleak outlook part, but that is easily justifiable: Everything that happens to these people is their own fault and, believe me, they make some stupid decisions. So with that said, you have to take it all with a grain of salt knowing that good relationships shouldn't be this way. This is the Hollywood way.
Granted, if you're feeling down, I wouldn't watch Closer. But if you're feeling introspective (ooh, ten dollars right there), I'd hazard a viewing and see what piqued a lot of peoples' curiosity about four very confused, intolerable, profane and potty-mouthed individuals at the end of their ropes.
Oh yeah, Natalie Portman isn't really hard to look at either.