Its a great product and can do a lot more than you realize. For $30 I got a software program that sets up a graphical interface, downloads to a wall module, a remote radio controller/IR controller-ti talks to a reciever to run the lights.
Can run into problems with signal strength and perhaps your neighbor can operate your lights. But there are easy ways around this.
The best source I have found for X10 is www.smarthome.com
in calif. I wanted a dimmable module I could dim over time and they pointed me to the right unit.
They also sell other x10 compatable products. Leviton makes a commerical product long used in office buildings.
And its a fun system to set up.