I understand the question regarding the single stage heaters but I don't have anything to compare them to.
When you first turn them on, they get very hot and then in a little while, they settle done to a very comfortable level. Another nice feature I've been told, is that with the manual (not electronic) switch is that when you leave them on, they come on as soon as you start the car and you do not need to turn them on every time like some other manufacturers.
Heated seat, auto climate and remote start..... awsome combo!!! Unless it's realy cold outside, I just turn the heat seat off after 5-10 min because it's a bit warm if you don't have a long coat!
I won't buy any car without it... unless it's a summer car!