Pros: Helps me plan power saving strategies and determine vampire power.
Cons: ...non yet.
I have used this device for a couple years now - helps me determine what actual power usage is from various devices and appliances around my home. I mainly use the "watts" and "Kilowat Hours/Clock" features. Easy to use. Small to store. It allows for quick tests for vampire and other loads, or you can leave it plugged in - to a refrigerator, for example - for a week or month.
I tested my fridges for a full month to get the various usage and power cycle loads captured over time - was very VERY handy for that.