Just in case you didn't know, Dead Man's Chest is the 2nd episode in a three-parter, and ends slightly abruptly with some major questions un-answered. It's also fairly long at two and a half hours.
These two points drop it from the otherwise perfect score it would have, because it was fantastic. Seamless transition between CGI and physical effects, so much so that I couldn't tell the difference. Loved Davey Jones (expertly played by Bill Nighy) and his crew's costume and effects. In places it is a bit similar to the first movie (Jack and friends race to find the one weakness of an unstoppable immortal pirate crew, sound familiar?), but since that was a cracking film, it doesn't matter so much. Top-notch performance from most of the actors most of the time as well.

Got one or two "wow"s out of me too, in particular the Flying Dutchman's surface-to-deeps transition and the Kraken attacks. The three way swordfight was a little slapstick, and some of Depp's lines are not as polished as they could have been, but he steals the show with some of his better ones ("Oh, I've got payment. Look! [BLAM!] An undead monkey!").

I feel this movie could have been edited down to 2 hours with little loss, and down to 105 minutes by dropping a little of the cinematography. Still well worth watching though, and it's probably worth re-watching the first movie (Curse of the Black Pearl) before you go in.
So-oo looking forward to the third part in the trilogy...