I like FlexWatt, what I don't like is the aluminum tape you need to use with it.

FlexWatt is fairly easy to use. You can order it pre-wired from most places. (I got mine from RBI). If you get it pre-wired all you need to do is tape it down using the aluminum tape, which takes some practice to get right. Then is has a normal electrical plug that you just connect to the thermostat. Place the prob, plug in the thermostat, set it and you are good to go.