According to a 1UP preview, GTA IV suffers from the same glitching and frame rate issues as its predecessors.
"You'll likely notice the same graphical 'quirks' that the series has dealt with since the jump to 3D. The same filmlike, grainy framerate exists and usually holds steady, but it can momentarily dip when things get frantic," the article says.
"There's some long-distance graphical fade-in as well as some street-level hazards that appear only after you hit them. Traffic will be nonexistent one second, then three cars deep when you rotate the camera back around, and then completely disappear when your wanted level gets to two or three stars (which is oh-so-fun when you desperately need a getaway vehicle)."
However, this time round, Rockstar has made attempts to veil them.
"But even these problems have been 'upgraded' in a sense for GTA4: An artistic application of filters hides some of the uglier character models, there's more types of cars to choose from, and overall, the feel of the city trumps any of the shortcomings we're familiar with by now. But you'll be able to see that in the screenshots and eventual videos."