Grandmastersexsay :
Don't die shrinks only increase profitability of chips and not performance?
Smaller CMOS transistors have lower gate capacitance which allows faster switching using less power and shorter distances reduces propagation delays between gates. Both of those factors should allow faster chips.
A fair chunk of those margins is lost to reduced core voltages which reduce CMOS gate drive voltage and the associated output currents leading to smaller switching time improvements than otherwise possible and most of the rest is spent on cramming extra logic between flip-flops to improve IPC - this would be the other reason (aside from TIM under the heat-spreader) why Intel's newer CPUs have generally lower overclock margins: critical paths got longer/deeper logic-wise.