Mark866 from our own forums has found that PSM3 has released tons of new info on GTA IV. Some of it we already knew, but most of it is worth posting.

• According to the journalists, the first hands-on minutes were enough to solidify their feelings of how the game is going to kick ass.
  
• Liberty City has more streets than any other game in the genre.
  
• You cannot enter every building. However, you can interact with most of them. Rooftops, stairways, fire escapes, partial interiors, etc.
  
• Niko will not be able to manage property, gangs or trade.
  
• Bowling, dart games, drinking games, strip clubs and night clubs will be available.
  
• The core of GTA IV is all about the human relationship.
  
• Sometimes, your contacts may call you during a hard mission to ask you a service. In this instance, you can choose between the mission or whatever your contact is asking. If you ditch your mission to do things with your phone contact, you may see consequences. Whether or not you will be able to replay the mission that you went away from remains to be seen.
  
• The new impression of seeing a next generation living, breathing city is absolutely stunning.
  
• The pedestrian population density changes between the place/borough you are in.
  
• If you walk around the street with a gun in your hand, pedestrians who have a phone can call the police.
  
• In one instance when Niko tried to carjack someone, the scared innocent driver sped away so fast that he hit two cars.
  
• During the first mission that the journalists played, they tried to carjack someone without a gun. The driver beat up Niko. Niko got beat up so bad that he ended up at the hospital.
  
• Pedestrians react in a very realistic way. The journalists said that it is as if each person in the game leads his/her own life.
  
• It took 15 minutes to go through 2/3 of Manhattan with a boat. It took 10 minutes by car to go through Brooklyn and Central Park.
  
• The cars can be destroyed very realistically. Every part of the car can bend and fold.
  
• GTA IV has a wider variety of mission types. The missions are more difficult than in previous games.
  
• The game is done. Most clipping bugs are gone. The game is super smooth in terms of frame rate. (Note: The game is not 100% done. It is not "gold" yet.)
  
• If you press the jump button, Niko can climb everywhere. In other words, wall climbing from San Andreas has returned. You can strafe on walls, too.
  
• There is a swimming club.
  
• If you have five stars, it's very difficult to escape from the cops. They are everywhere and they don't joke with you. They are smarter than in previous incarnations of the series.
  
• While in a boat, the sound effects are awesome. You can hear the sound of the waves that beat the front of the boat.
  
• With powerful weapons, you can shoot through the walls.
  
• The weather that was seen during the four hours of gameplay included fog, rain, sun and clouds. A variety of colors can be seen depending on the time of day.
  
• When you die, you pay 0 but you get to keep your weapons.
  
• When you go to jail after getting busted, you pay more than 0 and you lose your weapons.
  
• While you are drunk, it's very difficult to control Niko. The drunk sensation is perfectly done.
  
• When stealing a car from a pedestrian, Niko didn't get into the car before the pedestrian sped up. Niko held onto the car as the pedestrian glided along the road. (Note: It may have been the pedestrian holding on to a car Niko was in. The translation is sketchy.)
  
• Choppers with search lights are in the game.
  
• Women will striptease in strip clubs when you pay.
  
• Depending on the borough you are in, pedestrians may speak different languages. Italian, Chinese and those in the Bronx are different when it comes to language.
  
• Health kits are available only in buildings.
  
• Grenade and molotov cocktail sound effects are stunning.
  

Source: mark866, GTA-Like