Product Review (submitted on September 10, 2011):
The solar cell provided is, as with any solar cell, very sensitive to light. The motor however is very insensitive to the voltage supplied by the cell. Even in good sunlight, you will likely have to give the motor help to get moving. Then, once moving, the speed is only grossly responsive to the voltage from the cell. Direct sunlight will keep it spinning nicely. Reduce the brightness by much and the motor will slow to a halt. The supplied paper patterns are of no real use because the motor speed cannot be carefully varied enough to produce interesting optical phenomena. The spiral pattern either spins to a blur or the motor stops.
I dumped the motor and hooked up the cell to my digital voltmeter. In this way I have a very sensitive light-meter for the $10 price of this item.