they used to be popular long time ago when technology was not advance enough and laptops used to get hot with excessive usage. some models today do get hot with prolonged usage so if you think you need a cooler, get one.
I use a Belkin one & its pretty solid... Had a choice of either belkin or a chinese one which was so light it would have broken in half with the pressure of my fingers ... Got mine for 750 from Laminton but its listed for around 850/- on ebay..
I use Logitech n120 laptop cooling pad for my HP DV6 Running Core i7.its pretty decent one tho having a cushion support at the rear and a powerful (adjustable speed) fan placed with round air flow. my main reason to buy was i have a core i7 so i have a default cooling fan at the base of my laptop to prevent the quad core from burning when all the 8 cores runs at full speed.due to this i have to always ensure that this fan get enuf sir to it (especially when i play heavy graphics game on it). And the laptop get heated up at the base when there is no air flow at the base. so basically after using this cooling pad my laptop remains cool all the time (thanks to the efficient fan it got) and i can keep it anywhere on my bed and hours on my lap. and now it keeps running for days without shutdown.i bought it from Calcutta (city centre 1) at a HP store. cost me 1300 bucks. yeah its pretty costly but the others wernt much comfortable than this and it has proved to be. its has 2 yrs warranty. m satisfied n love it.it generally depends upon your use and handling conditions and laptop needs. if u feel so take a Belkin one around 750-800 i guess they are reasonable and gud.buy it from Flipkart. dont go for e-bay. my frnd bought it from there...and it seemed they gave a used one.hope all of u find this usefull.
It is not necessary if you're using a recent laptop and you use it like a normal laptop.I have the latest 13" MacBook Pro, which runs decently cool, but I use the laptop pretty much like a desktop (external mouse, keyboard and dual monitor setup), with around 15 applications running constantly. This type of usage will wear out the parts quickly due to prolonged exposure to heat. I use a Belkin cooling pad which brings the temperatures down by 3-4 degrees, a fair enough exchange in the long run.