APC certainly don't tell you. Here are the questions:

1. Why should you install this product when OS X has built-in support for UPSes which works with APC models. They keep on maintaining the product so they must think there's a reason, but they don't reveal what it is anywhere!

2. The About... dialog in the prefpane says: "PowerChute Personal edition protects your operating system by gracefully shutting down your system in the event of an extended power problem", but the Read me file says: "The OS shutdown performed by this application is an emergency shutdown. No applications are closed and no application data is saved." WTF? Which one is true???

Who knows? It would be great if someone from APC could comment, but I'm not holding my breath!