It got me to buy the full version

I didnt care for the stock sounds that it offered. However, you can customize the sounds on the "mix pad," which allows you to place the sounds (left, right, front, back and anywhere in-between). You can also control the volume, pitch, variance, and speed of each sound. You can even combine sounds with each being completely customizable.
I dont use the app for sleeping, just working. Other reviews say that your mac will no sleep with this on but doesnt that defeat the purpose?

This app is fantastic

ford_prefect1171 about White Noise Lite