Oh amazing. its like sinking into a cloud. Absolutely perfect for side sleepers and stomach sleepers. But if youre a back sleeper, I would go with the 2 in. You dont seem to have enough support in the lumbar  with the 3in. Theres too much plush. 
I will say that I dont think that the gel does anything to help with cooling. I think what matters more is ventilation and whether or not youre using cool sheets. Cotton is the best.