How much does the performance of the graphics card actually affect the 3D View?

A correctly set up graphics card makes a huge difference...

• subpixel antialiasing is standard on most cards these days, and when enabled, gets rid of jaggies very effectively, tricking the screen into thinking it is 4 times the resolution (4x4 = 16 x the # of pixels).
• OpenGL display lists lead to pan/zoom/rotate of complex 3D scenes in real time. Having said that, any recent graphics card probably fills the bill with adequate performance in this area. Just make sure there really is a graphics card that claims to be OpenGL compliant, at least to OpenGL 2.1 or later.