Mine doesn't leave any noticeable soot "stain" or anything on the driveway. I really get no smoke coming out of the exhaust at all. Of course I'm sure it depends on how old the car is, how the engine is holding up, etc... Mine doesn't have many km on it and it starts after about 2 seconds of cranking in -20 celsius overnight after 15 to 20 seconds of glow time (after the light goes out). Hopefully it will keep working so well!
The exhaust doesn't even have a diesel stink to it any more since I started using Sunoco Gold Diesel instead of whatever diesel I could find. It's only 2 or 3 cents more per litre and it doesn't smell at all. Seems to burn much cleaner and be more powerful. They do advertise it as having a higher cetane rating among other things, including cleaner burning. Seems to be great fuel. Anyone else tried Sunoco Gold Diesel?