Are there laptop coolers that actually produce a lot of air and make a real difference?

Just raising it helps some, but in general any newer laptop draws air from below and exhausts it from the sides so a cooler on the bottom doesn't do a lot for the laptop.

The exception is if you are resting it on a soft surface that could block vents, like your f-ing lap! In that case any of those coolers will make a big difference in both your comfort and the laptop. On a good hard surface that will make very little difference unless your laptop vents are clogged up as others have said.