After watching (and becoming an emotional wreck by the end of) Eternal Sunshine of the Spotless Mind, I set out to finally watch Charlie Kaufman's other works, starting with Being John Malkovich. And the experience was definitely not disappointing.
With this being a Kaufman screenplay, the characters are truly the star of the show. I can't stress how great ALL of the performances are in this film. Cusack definitely nailed his role at being an all-round unlikable asshole and deranged psychopath who would do everything to get what he desires. Likewise, Cameron Diaz was excellent in her role of an overly obsessive person, both in her passion for animals and her love life. I was left disappointed to see her sexuality not be explored in greater detail, but what little we have on screen is sufficient to portray a highly flawed but ultimately likeable character. Catherine Keener also gave a stellar performance as a highly conflicted figure: a woman who is cold, harsh and manipulative, but equal parts sentimental and hopelessly vulnerable. And of course, can't forget the titular John Malkovich in the role of his career. Going into detail would mean spoilers, but suffice to say, this is quite possibly the finest performance in a body switch-type movie that has ever been committed to film.
As for the soundtrack and cinematography, they're serviceable. Both of then did their job incredibly well in that they never felt jarring, confusing or incongruous, but don't come in expecting a Deakin+John Williams collab.
In short, film's great, and you should really watch it. You might not like the characters (especially Cusack's), you might not like how weird the film is, but it will be a very memorable experience regardless.