Yes I have heated seats :-) but they do take about 20 minutes to get really hot.
It seems they get a little warm after about 5 minutes, but then they turn off for a while and then kick back in and get really warm a while later. I think there is some sort of computer that controls them in a funny way. One of my staff likes to randomly turn his side off and on to get them to heat up faster.
I have decided I'll look into the diesel fired heater and see where that goes. The next car is definitely going to be a plug in hybrid.