There are some Bond films that can be accused of sticking rigidly close to formula. This isn't one.
You could call it 'The World is Not Enough' done right. A Villain with a close connection to 'M', MI6 being closed due to an explosion and a more personal assignment for Bond.
But on the other hand it feels unlike any other film in the franchise. Bond is usually the example held up to show how all those screen writing books are wrong as here is a character who doesn't change but Skyfall is one of the few to give Bond a clear character arc.
Bond is shot in the pre-title sequence and spends three months living the quiet life until he hears about a terrorist attack on London and decides to come in from the cold. He's bitter towards M who ordered him shot and in a training sequence we learn he is no longer the crack marksman he once and as one character remarks in "a young man's game" which gives it a similar tone to Star Trek II which also features a hero dealing with aging. With Craig having signed on for two more films its an odd time to bring such a subject up.
Overall it's a good film and a welcome return to form after Quantum of Solace but refreshingly different from the 'cookie cutter' formula that hold some of the series back.