I originally used this for an arcade cabinet where powering everything off from a single switch on the back could have caused problems for the pi. It works a treat and neatly shuts it down after about 20 seconds. I've got a second one that will be ideal for a portable project as well. The documentation is pretty comprehensive but thanks to the support team who've answered my questions promptly.
I've been using an AdaFruit PowerBoost 1000 but it doesn't quite provide enough juice since I added an extra USB device. The fact that with the PiVoyager I can monitor it and do a clean shutdown if required is a bonus.
In our use case, we have a Rpi zero that we want to operate in demo mode for a period of time and then turn off. It can be turned on again by pressing a button or at a certain time of day. We also wanted the Rpi to turn itself off, and come on again at a certain time of day. All this was accomplished by simply adding the PiVoyager, a switch, a battery and a little bit of code. Since the PiVoyager also monitors battery voltage, we can have the Rpi notify the user when it needs to be recharged. The PiVoyager takes care of the charging once usb power is applied. Great idea and implementation.