Last year, I didn't bother with it. Our engine is under the port settee (as seen in one of the pics below) and it stays plenty warm there since we have to heat the boat for us and the pets all winter anyhow. Winterizing really just helps things not freeze when you will be away from the boat, but we are never gone for long enough to care. We just leave a small heater on and have a friend watch in case the power goes out.
However, our engine is seawater cooled and winterizing has the added bonus of clearing the corrosive seawater out and replacing it with fairly neutral engine coolant for 4 or 5 months. That little bonus makes winterizing worth it to me, so today I changed the oil (done every spring and fall), flushed the system with coolant, put some sta-bil in the fuel tanks, and put some preservation gunk in the spark plug holes (is there a better name for those? I'm sure there is)
In this picture you can also see the 120 amp alternator we put on this fall. Our old 40 amp motorola was dead and even when it was alive it could barely put any juice into our battery bank, so I replaced it with this monster. Works great, and it's so clean and shiny! Made specifically to fit the Atomic 4 :)
Willie is never quite sure what to think when the cover is off of the engine.