I haven't had much to do with the C-BUS system, but I did look at using it when we did a renovation. After going through what the system could do I concluded that for our household MOST for the stuff was of no use. The stuff that was of interest could be done cheaper (much cheaper) by other means.
It seems that the C-BUS systems is designed to make the electricans life easy, not mine. However I have seen the C-BUS stuff used on industrial scale and it is very good (and cost savings make it viable).
For the household applications there other options. The phone and data points are easily done with cheap off the shelf equipment. The video and audio stuff likewise. Alarms are dirt cheap and reliable. The only thing that the C-BUS can do that is somewhat unique is control the lights and power, which it seems to do quite well.
In short it is my half assed opinion that C-BUS does its core function of power control very well. The add on functions don't come up to parr.
