I have a Robo-Kleen cleaner, it's powered by a transformer (that stays outside the pool) connected by a long cable. It has it's own pump the pulls water and debris from the pool floor into it's internal filterbag. It goes back and forth over the floor with some apparently random turns. It gets leaves and sticks as well as fine sand. It doesn't climb walls and doesn't brush. I'm on my second unit, the first lasted three years but I was happy enough with its service that I bought another.

As far as I'm concerned, it pays for itself each time I use it.