At first, it was hard to sleep on, but I'm lazy, and so I kept it. That was a good decision. Today, I have a much softer mattress, and let me tell you, I'm suffering.
Whenever I go camping in the summer, where I'm not in need of any insulation, I usually opt for just a simple, thin, foam sleeping pad, and it works wonder. The first couple of nights it's usually quite rough, not uncomfortable mind you, just hard to sleep as it's not as superficially comfortable, but after the initial acclimation my back's so much better.