Finally got around to seeing this the other day, and this might eclipse Julie Taymor's Titus as my favorite Shakespeare film. Laundry list!:
-The film is just gorgeous to look at, with rich colors and immaculate costumes. I also love the way Branagh reimagines famous scenes like "To be, or not to be...", Claudius' confession, and the play-within-a-play, or adds crucial intercuts like Claudius and Gertrude drunk on their wedding night, Hamlet and Ophelia's passionate (though brief and tasteful) sex, and the actual murder of King Hamlet.
-Branagh is on fire here, even in the quieter scenes, and he clearly relishes getting to play Hamlet's more sarcastic scenes or the famed "My thoughts be bloody, or else be nothing worth!" soliloquy. He's also unafraid to portray Hamlet as a bit of a douche at times, particularly during the nunnery speech or his self-satisfaction at witnessing Claudius' guilty face. The rest of the main cast is great too. Derek Jacobi (who I am always happy to see) makes Claudius both a great villain in his manipulation of others, and a surprisingly sympathetic soul as he tries to run a kingdom while his nephew's acting like a mood-swinging lunatic. Julie Christie makes for a marvelously ambiguous Gertrude; she's clearly in love with Claudius, so did she have anything to do with the king's murder? Christie never quite answers that, and I love her for it. Kate Winslet is so very sad as the doomed Ophelia, Michael Maloney is a passionate Laertes, Richard Briers is a terrifically manipulative Polonius, and Nicholas Farrell does some underrated work as Hamlet's only true friend Horatio.
-The celebrity cameos do vary in effectiveness, but most of them work. Brian Blessed proves to be intense and commanding even when whispering as the Ghost, Rufus Sewell is appropriately intense as Fortinbras, Billy Crystal and Charlton Heston are surprising highlights, it's always fun to see Gerard Depardieu, and even Robin Williams works as Osric. The lone exception is Jack Lemmon, who I love dearly, but just seems utterly lost with this language.
In short, I loved it.