I think it was well worth the trouble of installing. Definitely much, much better than no heater at all. I've found that combining the block heater with my 200-watt magnet heater on the oil sump works well.
At 0 degrees fahrenheit, with both devices having been plugged in for a couple hours, the car will start *instantly*, and the idle rpms will begin to drop within just a few moments after start-up. The engine is nowhere near operating temperature, of course, but the car is ready to drive much, much sooner than it would be otherwise. Best part is, the power usage isn't going on to my own hydro bill.
The real test will come when we get a wicked 30-40 below zero fahrenheit cold snap.
I decided to hang on to the Kats external tank heater I bought. Check out the vintage 1970's-looking packaging:
This thing wasn't very expensive, and maybe I'll be able to install it in my next car.