It's really really bad when playing Assassin's creed Brotherhood or Call of duty 4.
My system is
i5 750 2.67ghz with stock cooler
4GB of ddr3 1333 noname brand
GTX 680 EVGA superclocked
Vertex 3 120gb connected in sata 2
power supply 600w noname brand
Windows 8 64 bit pro (it doesn't have to do with that I'm sure of it)