Laptop cooling pads depend on the design of the laptop it self.
For example. I had an old Compaq with 2 fairly large fans(blowers) and vents for them on the bottom/sides. That thing would NEVER need a cooling pad(and it has a 89watt rated cpu. imagine the battery like of this thing
). As long as the feet of the laptop keep it off the surface enough to avoid restriction, You should be ok.
It is hard to say how much effect a cooling pad would have(because all notebooks are a bit different). If you plan to leave it at very high loads for extended times, gaming or video compression the pad may help to keep the full system a bit cooler.
I have notices an increase of laptops having the fan(s) draw air from both the keyboard side and small bottom vents. While this tends to look nicer, It makes cleaning MUCH harder if you let the dirt build up. This can happen rather fast in a laptop that is loaded often.
To get to this, the notebook had to be take right apart. This is why I recommend blasting air backwards into the exhaust vents(with the system off clearly) more often when the laptop is used for gaming/video encoding. Clearly this is worse with pets that shed hair/fur
Laptop makers like to push the temps as high as they can to keep things more quiet, or at least that seems to be the idea.