GTA IV runs at about 35-40 fps for me on all medium, view distance of 20.
i7 with 512 vram.
Make sure you have the laptop propped up a bit so the vents are clear. I know that was dragging down my framerates because the vidcard was too hot.
Lower than 30 fps seems a bit slow on low settings with that view distance.
The 330m gt is a decent card - not the best - but certainly doesn't warrant the generic "Apple doesn't care about graphics" refrain.