How effective are Laptop Cooling Pads ?

It depends, sometimes cooling pads can make the situation worse, using more power creating more heat then they can cool, they aren't normally worth it unless there very expensive ones. Cooling pads blow cold air towards the bottom of the laptop, the CPU and other important components are hidden deep inside the laptop, the cooler won't reach these, all it does is provide the CPU heat sink fan with cooler air then normal, but like i said, they can require more power (heat) to run then what they cool.