UPDATE - I installed the block heater in Jan.2005 and have to say that it sure is nice to have immediate heat - especially considering I leave the house most mornings before 6.
I will say that it was as difficult to remove the block plug as everyone would say it would be. I finally had to use an air chisel to get the plug bent enough to actually pull it out. The actual installation of the heater was easy and, so far, no leaks.