Today, the first Trailer of the game has been released. Mixed opinions fly!
Grand Theft Auto 4 official Site
Links to said Trailer:
So far what I've collected:
The main character is Russian, from what I can tell of his accent. It seems to be set in Liberty City, but it looks much more like New York than before in GTA3 and Liberty City Stories. The environments look MUCH more detailed than before, and that conclusion can be made even before we see any actual Gameplay of the game itself. I see dynamic shadows, bloom, HDR, Bump Mapping, good Water effects, etc. Basically a next-gen title.
Discuss to your hearts content!