According to PSW magazine, GTA IV is set to get custom music via the in-game mobile phone. It will play any music floating around on your PS3's HDD.
This coupled with Criterion's 'Burnout Paradise' update, shows that a way has been found to get around Microsoft's in game music patent.
How this has been achieved hasn't yet been revealed, but at least its looking up for Sony. Also announced were a few other small features of the game. When in public you can get the cops called on you if you are so much as brandishing a gun in front of them.
Mini-games will include: Bowling, Darts, Drinking games.
You can do multiple missions at once.
Different NPC pedestrians will be harder or easier depending on the type of NPC (e.g. an old lady will be easy to knock down, but mid-age men will be more likely to beat you to a pulp).
The game will feature wall piercing like COD4 with the more powerful weapons. The hospitals wont take your weapons if you choose to pay $100 for the privilege.
Some NPC's will hang on to their car as you steal it. A drink of beer will make you stagger around wildly and the screen will blur.
And finaly NPC characters will speak other languages each other.