[BrianG]

The AS adhesive is what I use too. It works well too because the heatsink is the same temp (or close) as the ESC. You do have to make sure it's where you want though since it's permanent.

With regular thermal compound you have to be a little careful. For one thing it is oily and tends to attract dust and dirt. Then, if it moves around (which it will unless you have it SOLIDLY mounted), the dirt and stuff will add more small scratches to the surfaces and also reduce the thermal conductivity. Also, after a while, some thermal compounds (like the generic goop at Radioshack), will dry out and not be as effective.