So I know this site has some mixed feeling about CVG and GTA 5 O'Clock, but I thought this was worth posting. They give you the actual interview audio (so it's not just CVG making things up) and there are a few interesting points in there.
http://www.youtube.com/watch?v=vBpTePVmdmg
Some points I picked up on:
Bullet proofing tires and roll bars will be available options for customization
Confirmed car impound (if your car disappears you can pay a fee to get it back)
Gas (petrol) trails that can be ignited to blow up cars
You keep your guns throughout the entire game, you do not lose them.
Free flowing fight system – more dynamic. No lock on required
Melee plays is more useful in big fights
Different enemy’s fight differently and use different tactics.
Hint at more destructible environments
Shooting stat will effect ammo capacity, reload speed, gun recoil, accuracy, combat movement