LongRunner,
This is quite an interesting topic.
In my normal day job (dairy equipment installation/repair) I deal with a lot of ELV stuff, by convention all control circuits must run off either 12V or 24V AC or DC.
I have a pet hate of SMPS equipment, in that you can put in all the protection you like, against power spikes and what have you, but if I had a dollar for every SMPS unit I'd had to replace over the years, I'd probably be retired now.
Give me a standard linear power supply, they run all day, every day.
I recall reading years ago, in a copy of Electronics Australia an article that mentioned that Sydney, Australia for years used a DC reticulation system and at the time that the article went to print, this system was still in use, I can't recall what voltage it used but I think it was in the area of 250VDC?, as you can probably imagine, switching something like that would have it's own problems with things like arc-quenching when the circuit was turned off.
