X10 has unit codes in addition to house codes allowing for many devices to work.http://www.x10.com/support/basicx10.htmI have used a ton of X10 but only install it at my own home for fun stuff or integration demos. If you only need to automate a few lights in a fairly small area, then X10 may work for you. Do not attempt to build a product or service around X10. X10 can be tough to implement whole house due to it just plain not working in some parts of a house (i.e. 1/2 the house). Also, noise in the power lines can turn on/off your devices in some cases. There are devices you can get to get around some of these issues, but they cost money and next thing you know, you have spent actual money on X10.The fixtures are usually very low quality and some have issues with the new compact florescent lights, I just removed my X10 switches for that reason a month ago.
X10 can be tough to implement whole house due to it just plain not working in some parts of a house (i.e. 1/2 the house).
I control my whole house through X10 with Arduino and it works fine - for me. I would never consider it "rock solid" however, but I don't need it to be.
The "1/2 house" problem was solved for me with a $14 repeater/phase coupler. As for dimmable CFLs I've yet to find a decent CFL that works with any standard dimmer.
Having said this, I never recommend X10 to 220V countries. The modules are 4X more expensive, so the "not rock solid but cheep" rule doesn't apply.
I don't get what does "1/2 house" means for you. Can you describe that problem?
What can you advice me for 220V countries?