WARNING: SPOILERS BELOW!!!! DO NOT READ IF YOU DON'T WANT TO LEARN CRITICAL INFORMATION THAT RUINS SURPRISES ABOUT THE MOVIE!
First of all, the opening title sequence, which the original Scream was so well known for, has been turned up to the nth degree. Using the movie-within-a-movie to fantastic effects the movie actually opens to scenes from the "Stab" movie franchise even though the audience doesn't know it. Several times you think you're watching Scream 4 but you're actually watching scenes from the fictional movies Stab 6 and Stab 7, which apparently use the same "movie-within-a-movie" technique as when the camera pulls back from the scene from Stab 6 it is into a scene from Stab 7 in which the characters are watching Stab 6. *Whew*
The cast is an all-start bonanza. You're recognize almost every character in this movie from the girls who die in the opener to the cops that are destined to die to the plethora of high-school misfits that populate this film. You can tell that the Hollywood talent really lines up to work with Wes Craven. The timeline has accelerated around 10 years from the original trilogy so characters have moved forward as well. Sydney is an author on a book tour who returns to Woodsboro. Dewey and Gale are married, Gale a retired reporter with struggles to write novels because of writer's block, Dewey is now the town Sheriff. There are probably a good dozen or so other characters thrown in as well and it's a good thing because the body count really stacks up.
Scream 4 really makes good advantage of advances in technology. You see characters using iPhones, laptops, and webcams in new and unique ways that just simply didn't exist when the other Scream movies were made. In this one, the murders are actually making a movie as they kill by using webcams to record everything. Who knew there was an iPhone app that made your voice sound like Ghostface's?
A lot of horror movies have come and gone between Scream 3 and 4. In Scream 4 the characters probably discuss or mention close to 50 other horror movies. Changes in the genre are analyzed in typical Scream fashion and then reflected on as the killers patterns their killings on these new genre trends.
Scream 4 really kept me guessing as to the identities of the killers. The red herrings are so strong that you actually have difficulty seeing the killers hiding right in plain sight. Also, as my wife can attest, it made me jump probably about ten times. Which is awesome because you KNOW its coming. Craven is a master!
In conclusion, Scream 4 is a VERY strong entry into the franchise. I would place it as the second best in the series, right after the original. What's great is they leave it open for future films. So my theory about Sydney's father being the mastermind behind all of the killers could still be true...