The other ones *work* but for my money/power consumption, nothing beats the freeze plug block heater, IMHO. As long as you're careful knocking out the frost plug (rather than knocking *in*) its not really a huge deal to install... easier on the 3.0V6 than it was on my 2.5TDi, I can tell you that!

I've had the inline coolant hose heater as well, but it didn't do near the job. The pad type are okay as supplemental oil warmers, but the frost plug type heats the coolant directly in the water passages... in winter it turns my truck from a rattly-smoke-machine to a smooth....well... okay still rattly... <img src="/forums/images/graemlins/lol.gif" alt="" /> less smoky, start-on-the-first-turn kitten.

As always, YMMV.