from what I understand, these things are really only useful if you are actually using them on your lap. if you are just like using the laptop on a desk, simply elevating it a bit (with either a stand or a stack of magazines) will do wonders with preventing your computer from overheating though.
This, only I used lego bricks to hold it up.
Also don't get a Belkin cooling pad, I had one and it gave me trouble non stop and then finally died a few months later.