Mapawatt has purchased and tested this product and recommends it for all users. 

The Kill-A-Watt has more capability than other appliance energy monitors like the Belkin Conserve Insight Energy Cost Monitor in that it can measure total kWh consumed, power factor, VA, and frequency (Hz). However, unlike the energy monitor from Belkin, it doesn't have a cable connecting the screen to the measuring device. This makes it difficult to read the LCD screen as the electrical outlets that your appliances are plugged in to are not usually in the most convenient places.

The Kill-A-Watt is a bare bones device to help users understand how much electricity their 120 V devices use.  It can't send the data to a computer, but for those who need to understand how much electricity common household devices use, it is a great device.