I didn't see it as overacted (though it certainly wasn't subtle, lol)
I did raise an eyebrow at Julia Roberts trying to do something proper serious, though she wasn't atrocious
Natalie Portman was not right for the part imo, not at all
Jude Law, he is so shallow, he wasn't believable as the deep, damaged, desperate character
Clive Owen was good i thought but then i like his acting style. The scene where he is telling Jude Law that he knows he cries in his sleep for his mummy really stuck in my mind.
I remember seeing it at the cinema and wanting to get the 17-yr-old girls coming out of the cinema together and tell them that adult relationships are not generally like that (well, not in my life).