GTA IV for the PC offers offers some significant graphical improvements over the console versions, if your system can handle it.
As with many releases, there have been some post release issues, and this GTAIV Patch is designed to take care of them.
GTAIV Patch annotates the graphics options menu to include more effects parameters, such as reflections and shadow quality. Controller support has been expanded for a variety of gamepads and wheels, and there are a number of crash fixes and multiplayer tweaks.
Of course, with a game as expansive as GTA IV, the odd glitch is inescapable, so users should keep up to date with Rockstar's GTAIV Patch.