I just wanted to comment on this discussion...
Yes, the X10 stuff is very addictive. I'm carrying a balance on my credit card, but last night I still had to use my $20 coupon (of course, I had to bump my purchase over $25 for the free shipping, heh). At home I use the tranceiver for my halogen torchiere, an appliance module for a fan and a wall switch in the bathroom. I use either a keychain remote or their 8 in 1 universal remote. I also set up my GF with one of these remotes, as well as the x10 credit card remote. A tranceiver for a heater, lamp module for bedside light, appliance module for a halogen torchiere. Besides all this, I have about 5 more lamp modules, another appliance module, a 3-prong appliance module, tranceiver, two more keychain remotes, the firecracker remote pad, firecracker serial port controller and two more wall light switches... all unused. And what do I do? Buy more stuff last night. I got another tranceiver and a mouse remote kit. Free shipping, $20 off the order, two free micro keychain remotes... all for under $15 on my credit card. Crazy. I am looking forward to it, though. Wireless universal remote that doubles as a mouse for computer and triples as an x10 remote... yum! Also, the micro keychain remotes are about half the thickness of the one I use and has 2½ times the range.
I use my setup mostly in my room, and have no problems. Once, during a LAN party (hosted in my living room) I set up a few fans with the x10 stuff to cool us off, and I had major problems with it not responding. Yet, since the LAN party, I've been using the same units in my room (for about 1/2 year now) daily without problems. I think for the people having intermittent problems, perhaps it could be interference from other equipment (in my case, 10+ computers in one room).
I think their "Free" firecracker deal (with $5.90 shipping) is dead after all this time. They now have it regular priced at around $50, and a special for new customers with $10 off. Though I'm poorer for it

I'm glad I got the "free" kit.
I don't have any experience with their surveillance and audio/visual components, so no comment there.