To answer the original question of if heatpipes are up to the task of cooling modern CPU's the answer is yes, they are capable enough assuming they have been designed correctly.
Heat pipes are designed for what amounts to a wattage window.
Where there is an optimum range of heat dissipation at one end of a heatpipe and cooling at the other.
Give a heatpipe too little heat and the C/W* rating suffers a bit.
(*degree Celsius rise per watt of heat input)
Give a heatpipe too much heat and the C/W rating
really suffers a lot.
Remember, heatpipes are designed for a given thermal load.
http://en.wikipedia.org/wiki/Heatpipe
The materials and coolant chosen depends on the temperature conditions in which the heat pipe must operate, with coolants ranging from liquid helium for extremely low temperature applications(boils between 4.2 and 3.2 kelvin#) to mercury for high temperature conditions(boils at 630 kelvin#). However, the vast majority of heat pipes uses either ammonia or water as working fluid.
...
Heat pipes must be tuned to particular cooling conditions. The choice of pipe material, size and coolant all have an effect on the optimal temperatures in which heat pipes work.
When heated above a certain temperature, all of the working fluid in the heat pipe will vaporize and the condensation process will cease to occur; in such conditions, the heat pipe's thermal conductivity is reduced to the heat conduction properties of its solid metal casing alone. As most heat pipes are constructed of copper (a metal with high heat conductivity); an overheated heatpipe will generally continue to conduct heat at only around 1/80th of their original conductivity.
Bold added for emphasis. Bold italics added by me.
#Numbers given for 1 atm pressure.