New features based off the trailer:
1. You can open car trunks - we already knew this - but it seems that you can store weapons in there.
2. Cops don't swarm after you and instantly know where you are. You have to be seen in order to be chased after authorities. They also use actual tactics now, such as splitting up into teams.
3. You can now rob banks at your leisure.
4. You can now kick down doors. This is good news, because you may find some useful hideouts while on the run from the cops.
5. You can now see the road behind you via rear view mirrors.
6. Environments are more interactive. Anyone who has spent considerable time with the past 3d games know that they have gas stations. You could blow them up with a simple shotgun shot, but now, you can simply send a car into them. Real time car damage is also included.
The Yahoo! preview from last night said that time will be more important in the way you do missions and the like and this will be hinted at in the trailer, but I haven't found anything yet.