Gaming is really the driving force behind faster vid cards, especially on-line gaming. Framerate is Life!
Faster framerate means that you have a cleaner, clearer picture even during fast motion like turning your head/body, so you're more apt to see that gun barrel sticking out around the corner before it blows your @$$ off.
If you don't play games much, like me, then you don't really need the latest card, unless you just want to have the highest 3DMark score in all the land.