The nice thing about X-10 is that the protocol is simple and there are lots of devices that work with it, most of which are relatively inexpensive. It's also friendly to the home hobbyist, and the hacker, since you can buy interfaces that will hook up to your PC via a serial port and write your own scripts, or download free software like Misterhouse.
If I can't turn my outside lights on at sunset via a script, then turn that script into a cron job, don't even talk to me about it. I'll write the interface myself, just give me a clean API I can code to.
We hate it when Microsoft or Apple take the attitude of "No, we won't open up our API and play nice with the open source crowd. At best we will make you join our developer program and sign an NDA. At worst we won't talk to you at all."
When the home automation vendors do it, they're no better. They don't deserve our respect or our help.