I have one...its a piece of crap. The way it works is that the tip of the iron is actually two small electrodes - when you touch it to a metal object it completes a circuit and current flows through whatever you're trying to solder, causing it to heat up. The tip of the iron doesn't actually heat up at all (except for heat transferred from whatever you're trying to solder). There's no way to control the temperature, the temperature will depend on the resistance of what you're trying to solder, and the thing usually makes a few sparks when you use it (so you wouldn't want to use it on delicate ICs). Plus the tip that comes with it is too big for any kind of delicate work.
I found it was almost impossible to maintain good enough contact between the tip & what I was trying to solder to get it to heat reliably. It also runs on AA batteries, so I can't imagine that they would last very long (I measured the current at just over 2A, so it will probably suck the batteries dry after just a few uses).
