Here are some new screenshots of the PC version to whet your appetite. They appeared online this evening at GameStar.de (12), PCGamesHardware.com (13) and 3DJuegos.com (15):

GTA IV PC Screenshots (13) at PCGamesHardware.com
GTA IV PC Screenshots (12) at GameStar.de
GTA IV PC Screenshots (15) at 3DJuegos.com
GTA IV PC Screenshots (100) at Cynamite.de

Thanks to Freezer89 for the heads up!

Update: Games site Cynamite.de posted a massive gallery of 100 hi-res screenshots as well.