I have used several brands of electric kistka over the years and my personal opinion is that the best one is from Wax Art Supply.
This brand was designed by a mechanical engineer and it really shows! The tips provide a consistent wax line that rarely skips or clogs up. They have a great selection of tip sizes from extra heavy to triple extra fine. The tips I have used the most are the fine, double extra fine, medium and heavy. It has tremendously helped my artwork as I can now get all those lovely and amazing details that are in my head onto the egg. In addition to the different tip sizes, you can also buy either a fixed tip or an interchangeable tip that has a small screw that holds the tip tight. As a testament to how great these tools are, I used my grandmother's Wax Art Supply interchangeable tip kistka that she got sometime in the 80's (it could even have been the 70's!) until it finally died last year in 2009 - that's at least 20 years.
Please take a look at them if you are in the market for an electric kistka. I know you will be happy.