* L1/LB speeds up the players actions. The developers call it the “awesome button”. Tired of waiting to hijack a car? Use L1/LB to missile kick into the driver’s seat.
* There are no more hamburgers, liquor, etc. for health regeneration. Health will now regenerate on its own much faster.
* There’s one mission in the game where you take control of a tank falling out of the sky.

Other stuff i saw at the SR forum:
-Weapon Customization
- CoD Modern Warfare 2-Style Predator Drone air strikes
-Gun which allows you to hack into vehicles and either hijack them with their driver still inside, or use them to control them like UGVs(Unmanned Ground Vehicles)
-Steelport ONLY, no Stillwater
-you will target the gangs by taking over their criminal rings, which is the new way of completing activities
-drug dealing/prostitution activities: - controlled by luchadores,.
-security/money laundering activities: - controlled by the deckers.
-Mayhem: activity - controlled by syndicate
-STAG i guess is our new form of law, which could account as the swat or military.
-gang colors are back, morning star are red, luchadores are green, deckers are blue and saints are purple again.
-Theres some new wacky diversions and activities, one of them involves driving around with a tiger in your car ala ricky bobby style! and some crazy japanese gameshow that pits you against rival syndicate members in a survival of the fittest running man course.
-you have a huge golem as a homie, these freaks are failed cloned experiments, so while he's stupid, he's very freaking strong.
-there's also another diversion called "tank mayhem"

-The RC gun where you're able to control other cars can be upgraded later to control tanks and air vehicles. You assume full control just as if you were inside the vehicle. One example is strapping satchel charges to the car as you run it into a gang. You can also get gangs in trouble. Take over a gang car and start ramming police cars, the police will start attacking that driver/car.

-Weapon upgrades: One example is an assault rifle with a sniper scope and a grenade launcher. You can add a third barrel to a shotgun, called the gravedigger. Upgraded weapons are permanent so you never lose them.

-The "awesome button" (LB, also sprint). Carjacking someone from the side and pressing LB will send the driver flying out the other door. From the front you'll leap over the hood and smash through the windshield kicking the driver in the face. Carjacking them the normal way makes the camera zoom in as you either shoot them or slam the door on their head.

-Grenade (or other explosive) has its own button now, Right Bumper. So you still keep your primary weapon in hand.

-Activities: "Tank Mayhem"- You're given a task to destroy high value targets. It also shows off the technological improvements. cars warp and deform instead of just exploding on contact. health pick ups repair your tank.

"Guardian Angel"- Drive around carefully as a tiger sits in the backseat. Bump into a lightpost or take a sharp turn and it'll start mauling you. If you're playing this in co-op, your partner must assault the tiger to keep him out of your hair.

-Mission where youre skydiving in a tank has you shooting at other tanks as well.

-All weapons have their own "nut shot" animation. Like holding a bazooka and performing a melee will make him swing it like a golf club.

-car surfing is back.