I thought I might share my experience with X-10 based home automation systems since it is the largest part of my business.
With the use of multiple amplified phase couplers, X-10 based home automation systems work very well in homes well over 5000 sq. ft. Specially designed phase coulplers can be linked together to work together in large homes without conficting with each other.
Also, I primarly use JDS Technologies, X-10 based home automation controllers. The Active Home product marketed by X10 isn't anything close to the JDS controllers. Many people get frustrated with the limitations of Active Home, but as you pointed out it, it costs less than $40.
JDS controllers range from a little over $300 to a little over $1000. The flagship product, Stargate, integrates X-10 control, telephony functions (voice mail with up to 8 mail boxes, Caller ID, paging, call forwarding, etc.), 16 digital inputs (motion sensors, rain meters, etc.), 8 analog inputs (temperature sensors, humidity sensors), 9 relay outputs (irrigation control, etc) 2 RS232 (serial) port outputs to both read and send ASCII to communicate with other products such as alarm systems and text paging services, and an RS485 port that allows connection of 16 other RS485 devices (thermostats, LCD control panels, etc.). The number of inputs/outputs can be expanded with optional I/O expander boards.
There is also an optional bidirectional IR controller that will learn up to 500 IR commands from exisiting IR remotes. This product is integrated with the Stargate controller. For example, you could press "123" on any IR remote and Stargate could respond by announcing "Home Theater Mode", dimming the lights, turning on your IR components, etc. It has 4 zoned IR outputs on board. You could also pick up any telephone in your home and press "CNN" to turn on your TV and watch CNN.
The Stargate runs completely independent of the PC. It has digital memory for the storage of up to 40 minutes of speech, and the firmware has hundreds of prerecorded words and phrases that can be constructed into speech for verbal confirmation. The verbal confirmations can be routed through the line-out (for an amplified speaker system), speaker out (for direct connection to several speakers), CO line (e.g., a hold message while a call is on hold), or the Intercom (e.g., to speak with someone at your front door).
The Stargate allows 6000-8000 lines of code with complex (nested) IF/THEN statements, macros, timers, flags, etc.
On our web site, we have some downloads (click on the downloads button) provide more information. We have a document that contains actual Stargate applications, and we also have some PDF files with the product's specifications.
RCI Automation[Link: ourworld.compuserve.com]