I agree with Brian H and the rest. Now that I have X10 filters on all of my computers and plasma TVs, a phase coupler installed, and modified my CM15A to add an external antenna, I have great range and reliability. My wife loves it, and I keep adding more functionality. Her favorite to show off to company is our motion-activated powder room. Our cream-colored onyx sink is underlit (I took a set of halogen lights and installed them under the sink) and it turns on automatically when someone goes into the powder room. We just added an 18 inch high fountain, which also starts with the motion activation, providing a pleasant "tinkling" sound. My favorite is in the home office, which has a hard-to-reach light switch. Now, when you walk in, the motion sensor turns the office lights on, and they stay on until you leave. Very cool.
The attractive entry price point of X10's stuff gets lots of people to try it out. There's a second investment in X10 filters and phase couplers that you pretty much have to make to get things to work right. The third investment is when you fall in love and start adding more things. All in all, I probably have $400 or so invested. I control five sets of landscape lighting, a waterfall, and a fountain, plus a bunch of interior items. My wife loves being able to turn things off and on using a Palm remote. Very convenient.
I have a friend who does custom home automation for HUGE houses (10,000 feet and more), and his systems start at tens of thousands of dollars. For us average Joes, X10 is pretty sweet.
robster