This is probably my favorite Mission: Impossible movie since the first, although I may have to re-watch 2 and 3 to be sure. The villain isn't as memorable as Phillip Seymour Hoffman, but he wasn't in part 3 nearly enough.
The plot this time around is very familiar. We have seen it in several James Bond movies and in The Sum of All Fears. Someone wants to detonate a nuclear bomb, tricking the United States and Russia into declaring war on each other.
Despite the familiar plot, the movie is very enjoyable. The action set pieces are exciting, especially the sequence where Ethan Hunt has to climb up several floors outside the tallest building in the world. You really should see this movie in IMAX to get the full effect of this sequence. It was so realistic it gave me vertigo.
Another improvement in this movie is Simon Pegg. He appeared in a few scenes in the 3rd movie. This time he has almost as much screen time as Tom Cruise. More Simon Pegg always makes a movie more enjoyable.