This is a simple solution to taking photos at specific intervals with specific shutter times.
The Good: - Good value - Simple to use - Does exactly what you would expect -Backlit screen
The Bad: - No power on/off switch - Doesn't have any on-board memory to keep previous shooting settings.
I use it effectively to control my Canon DSLR for wide field astrophotography. Simply program the timer to take a series of long exposure images, point the camera at the sky and press the start button.
The back-light is perfect for night time use, and there is also a manual shutter button for quick checking position and focus.
The timer runs on two batteries, and the only way to turn the device on or off is to physically remove the batteries, which is kind of a pain. A cheap switch would make this device that much better and more convenient. The simplicity of the device also means no on-board memory. So if you set up your shooting sequence and then remove the batteries, you have to set it up all over again.