GTA4.net has some new info. The new info is from a 16 page GTA Special/Preview from Edge Magazine and someone from the forums over there posted the following:
http://www.gta4.net/news/index.php
* In GTA IV there are strip joints and, more unexpectedly,
comedy clubs, which have been incorporated in a manner that is "enough to make your head spin." Edge aren't allowed to say anything else about it at the moment.
* Jets and planes fly through the airport, and have visible pilots inside them. The tester drove alongside a jet, only to have a 4-star wanted level appear!
* One encounter face-to-face with a cop got the response: "I'm a cop... and you're a dickhead!"
* On the subject of multiplayer... Houser wasn't able to go into much detail, but
he did mention being able to get together online in the game with no other goal other than to use it as a meeting place: "I'll meet you in a car and we'll hang and just drive and listen to music, chilling in the car, with your 3D model sat next to me," he says.
* The car paint jobs are noticable from newer cars being gleaming and spotless, to old cars being rusted and dull.
* Bulletholes and dirt are permanent on cars.
* Interior walls can be greatly damaged, "ripping chunks out of the plaster with gunfire."