Thermal compound is very important when it comes to running a cool computer. It helps to facilitate the dissipation of heat from the processor to the heatsink. Without thermal compound, it doesn't matter whether you're using stock cooling, high end air cooling, water cooling or above, cooling performance will be dismal. In the past few years, thermal compounds have undergone an evolution. I'm sure many are familiar with the basic silicon based thermal compound, also known as white goop. This quickly evolved into metal based thermal compounds, which by its namesake have a composition of metal particles. This improved the thermal conductivity, but also had the problem of being electrically conductive.
Now we are at a stage where performance thermal compounds are ceramics based. Thermal conductivity has been improved even more, and don't have the problem of being electrically conductive. Most of the thermal compounds we are looking at today are ceramics based.
The thermal compounds we are looking at in our mini-roundup are the Stars-700, Noctua's HT-N1, Arctic Silver's Ceramique, Tuniq's TX-2 and OCZ's Freeze.