The German edition of GamePro recently provided a full preview on GTA IV to readers in that country, but as you'd expect most of the information is already known to us. It did, however, provide a small amount of information, listed below:

• There will be several different animation sets for breaking into a car, so far we know one of them includes Niko breaking the glass of the window with his elbow, then starting the car using the injection cables. We know there probably isn't a lot of different other ways Niko can do this, but we suspect it will involve dynamic animations, and for instance Niko sometimes becoming suspicious in the middle of hotwiring a car, looking around to see if anyone suspects what he's doing, then continuing. Rockstar previously said they want the animations to look less "canned", so this would fit well with that goal.
• According to the article, Rockstar are using less non-realistic elements than previous GTA games, such as arrows and markers assisting and indicating things to the player. We already know the in-game mobile phone will play a big part in replacing some of these things, so perhaps we might see other helpful gadgets such a GPS system, though that is just speculation.
• One of the ideas going into development is to give every street in the game a name, which could be displayed on-screen when you enter it by foot or car. This feature is yet to be decided on, along with the previously revealed information piece about Rockstar still deciding whether the entire city will be accessible from the start, or if different areas will be inaccessible by way of cordoning off bridges and such.
  
  EDIT: After we received a full translation of this issue, we learned that every street in the game will in fact have a name assigned to it, and will be shown on your HUD when entering it. This will play a big part during missions, as for instance you might get told to go to a specific address. R* is still deciding whether or not they'll use colored markers to point addresses and such out to the player.
• When R*'s Dan Houser was asked about the differences between the Xbox 360 and PS3 versions, he replied saying that it is their goal to have none, and that there are no platform preferences, both are difficult to develop on. For now, we take this as to have nothing to do with the extra downloadable content.
• Speaking of which, he further says that they're not sure what exactly will be offered through additional content downloads. He says that maybe some things will be free, and others offered at a price.

Thanks to GTAReactor for help on translating the information.

Related: GTAForums