I've got one too, and I agree with @Ridgerunner in that it's a great tool in the arsenal but hardly the only one. I also got a couple of smaller ones, that are for mice, and I've had good luck with them too but again, I keep out a variety of mouse traps and devices. I bait mine with a dollop of peanut butter which I have rolled in rolled oats, so that I can pick up the pellet and put it in the trap. I have found that when I renew the bait I get a better catch rate. I've also had great big insects crawl into these traps and drain a great deal of power out of the batteries, meaning the batteries need replacing. Still I am happy with them and think they do a good job.
One I really like is made of grey plastic and I think they call it a "better mouse trap" on the packaging. It has a good spring on it, which wears out after time, but I've had them catch about 30 mice before they are really worn out and need replacing. These are nice in an area where you aren't worried about the trap being moved. One nice thing about rat and mouse zappers: they CAN NOT move those traps. Other types of traps can be moved and that can get inconvenient.