There's a new 10-page preview up at gameplayer with loads of new info about GTA IV. They go into detail about several new characters, the Rainbow Six-style combat, and how the Euphoria Engine physics help Niko to get drunk!
"F***ing awesome! There, if you wanted the quick two-word summation of the Grand Theft Auto IV demo we just witnessed, then that's it. Want three words? How about: best game ever."