X10 has been around for a long time, so it has the advantage of age, but in many installations it runs into a lot of reliability problems due to its susceptibility to noise on the electrical line. Its signalling rate is also quite low, so large installations degrade due to lack of bandwidth.
There are lots of newer / more modern standards that have emerged over the last few years. There are "open" multi-vendor protocols with shipping devices and controllers: UPB, Z-Wave, CEBus, and Zigbee are the main ones I can think of in that category. There are also some single-vendor protocols out there such as Smarthome's Insteon, Lutron, OnQ, and several others. Some are designed for retrofit installations, others require extra wires and are therefore mainly suited for new homes or major renovations.
As good as DHC is for learning about most things around the home, if you really want to get detailed information and answers on HA, the best forum is probably
www.cocoontech.com. The key contributors there maintain a home automation technology comparison spreadsheet that lists the features and capabilities of most of the key players. Anyone can view it at
http://spreadsheets.google.com/ccc?k...e9TIQhdA&hl=en
Sometimes the selection is driven by your choice of automation controller; people often pick the controller first and then go with one of the types of automated switches their controller supports.