This is a comparison between the leaked pilot and the officially aired pilot. Both have different scenes, dialogue, actors, soundtrack, etc. I have not listed the changes in music in this overview, because there are a lot of changes and differences. This sums up the changes in scenes, actors and dialogue.

PILOT
Leaked Pilot	Official Pilot
Sarah picks up John in Highland High School.	Sarah picks up John in R. Hadley Public Library.
Sarah picks up John out of his class.	Sarah picks up John out of the library.
The door is already open (via a cut).	Sarah opens the door.
Sarah and John run through the corridor.
	Extra shot of John in the police car.
	Extra shot of a police car being shot.
	Some extra shots of Sarah in the back of the police car, whlie another police officer opens fire at the Terminator.
Highland High School in the background.	R. Hadley Public Library in the background.
Sarah and her fiancee Burke Daniels. Plus alternate dialogue and scene.	Sarah and her fiancee Charley Dixon. Plus alternate dialogue and scene.
Different title screen.	Different title screen.
Different font in title cards.	Different font in title cards.
Extended bit of dialogue. John: Mom, how many times have I told you? It's freaky when you do that? Sarah: Sorry. John: What time is it? Sarah: It's almost nine. John: You're going to be late for work... What's going on? Sarah: We can't stay here John. John: What? Sarah: It's not safe.	John: Mom, how many times have I told you? It's freaky when you do that? Sarah: Sorry. John: What's going on? Sarah: We can't stay here John. John: What? Sarah: It's not safe.
Sarah's fiancee Burke Daniels.	Sarah's fiancee Charley Dixon.
Different fiancee, different cop, different room, different photograps, different bits of dialogue.	Different fiancee, different cop, different room, different photograps, different bits of dialogue.
Different photograph and fiancee name.	Different photograph and fiancee name.
Different photograph and fiancee name.	Different photograph and fiancee name.
Different font in title cards.	Different font in title cards.
	Quick extra shot of Cameron Philips jumping in front of John to catch a bullet.
Quick extra shot of confused and terrorized students before the line "Class dismissed."
Extended scene of waitress Sarah, also a bit more news on the tv.
Extended scenes of John running and hiding behind cars, before he falls on the ground in front of Cromartie.
The turn with the car happens after John looks at Cameron's wounds and realizes she is a Terminator.	The turn with the car happens before John looks at Cameron's wounds and realizes she is a Terminator.
Complete new scene with agent Ellison talking to deputy about the school rampage and where he notifies an extreme amount of damage done by just one person. Deputy: Found the science teacher. Very dead. Ellison: What about her? Deputy: She blew the dinner. End of the win. Know why anyone would wanna kill that boy? Ellison: No. Deputy: Well, someone wanted to kill that boy. Ellison: Damn.
Sarah tries to phone John but she can't reach him. She takes her binoculars to take a good look at the school.	Sarah is already watchin through her binoculars.
John is not visable onscreen when Cromartie phones him. Some alternate dialogue: Cromartie: John? John: Hello. Mom? Mom? Cromartie: I tried to call you. John: I have been trying to call you. Mom, it's back. God, all these kids. Cromartie: John, slow down. Where are you? John: I'm going to the house. Cromartie: I'll be right there. John: Mom? Cromartie: I love you. Stay right there.	John is actually visable onscreen when Cromartie phones him. Some alternate dialogue: Cromartie: John? John: Mom? Mom? Cromartie: I tried to call you. John: I have been trying to call you. Listen to me, okay? They're back. Cromartie: John, slow down. Where are you? John: I'm going to the house. Cromartie: I'll be right there. John: Mom? Cromartie: I love you, John. Stay right there.
Some extra lines of dialogue by the deputy: Ellison: 19 hours. Deputy: What the hell happened here? Like why don't we have any bodies? Where's the blood? Ellison: 22 witnesses, deputy Rich. 22 of your good townfolk. That's a whole football team.	Ellison: 19 hours. Deputy: What the hell happened here? Ellison: 22 witnesses, deputy Rich. 22 of your good townfolk. That's a whole football team.
John is almost crying in this scene.	John is definitely not crying in this scene.
	Complete new scene. John: Chip? Cameron: Back at school, you apologized for lying to me. So I should apologize for lying to you. John: It's alright, I get it. You needed to get close to me. It's just the way you are programmed. Like some hot girl is really gonna try to make friends with the new weird kid. If I'd thought about it, I would have known something was messed up. You know? Cameron: In the future, you have many friends. John: What model are you? Are you new? You seem... different. Cameron: I am. Sarah: Let's go.
Different font in title cards.	Different font in title cards.
It shows Sarah, John and Cameron sneaking to Dyson's home, and a different font in the title car. Also, Sarah gives a voice-over: Sarah: Two years ago, I had to tell Miles Dyson his research at Cyberdyne would lead to the birth of Skynet. I had to tell him he was the unknowing father of a nuclear apocalypse. He refused to accept his fate and died trying to change it. And if I am to have any chance of tracking down Skynet again, I have to tell his widow that even Miles changed his own fate... he didn't change ours. Sorry Miles.
	Complete new scene. While escaping from Cromartie at Dyson's, Sarah is shot in the shoulder. Sarah drops off John in a store to get some bandages and alocohol, while she and Cameron find a hiding place. She there tells Cameron to close the wound with needle and threads. She realizes that she can't keep on running anymore, because then she will lose John because he will leave her.
Extra bit of dialogue: Sarah: Tell me what's going on. Cameron: We're making a withdrawel. John: Do you have, like an account, here? Cameron: Safety deposit box. Sarah: When did you open that? Cameron: 1963.	John: Do you have, like an account, here? Cameron: Safety deposit box. Sarah: When did you open that? Cameron: 1963.
Quick extra shot of a police car arriving.
The whole order of events is different during the time discplacement scene when Cromartie enters the room.	The whole order of events is different during the time discplacement scene when Cromartie enters the room.
A quicke extra shot of our trio in the time sphere.
A quick extra shot our trio running away naked.
Sarah's fiancee Burke Daniels.	Sarah's fiancee Charley Dixon.
Different ending; Sarah, John and Cameron are preparing and storing weapons.	Different ending; our trio is outsied their new hiding place.