There are always a few people that say they have no problems with the game whatsoever, getting 60fps, etc. Hitting 60 FPS in GTA IV is not difficult especially with a modern gpu, you'll probably get over 100fps in some places. The issue is keeping a constant framerate. Which I seriously doubt ANYONE can pull off, no matter what pc you build and no matter how much you try to "brute force" this game. I have done so much tweaking, commandline, launch options fixes, i've looked for any possible solutions for stuttering/low framerate and completely exhausted any good resources I found on forums and through google. I've ran this game on multiple builds of my own and did a lot of asking around, and everyone has the same issue where the framerate drops to <45 in some places, or while driving. It is like that no matter how low/high your graphics settings are. Sure 40-100+fps is playable, but it's not acceptable for a game that's nearly a decade old... If anybody can run this game at a true constant 60fps, please show me, cause I honestly don't think it can be done.
Still a great game though.