I've got a brand new XS1000 UPS hooked it up to my G5 (10.3.2); was glad to see a panther compatible version of this software. It lacks any detailed information (like the PC version of Powerchute), but it does its job; here's a detailed rundown of what it does, since there was essentially no Mac info in the manual.

As far as options, it's very basic, but has what you need: Adds a preference pane with your choice of either shutting down after X minutes without power (preserve battery) or with X minutes remaining on the battery (longer runtime). Requires an admin password to make changes, not surprisingly.

If it does not detect a UPS, it'll pop up a window complaining (even over the login window, in fact). If a UPS then becomes available, it pops up another window saying so, so you'll know if your UPS is being monitored.

I did some tests, and on a power outage, you'll immediately get a popup window saying that the power is out, and your Mac will shut down at about (whatever time). My Mac woke from sleep immediately when the UPS kicked in, even though the UPS was connected to a USB hub (this is good, of course).

The Mac shuts down after the specificed period (not terribly gracefully--no saves occurred in open programs), and the UPS will power itself off about one minute after the shutdown process begins (this is NOT documented anywhere I saw), presumably after the Mac has finished shutting down (mine had been done for 40 seconds). If power comes back up before shutdown begins, the UPS switches back to AC and the software lets you know power is back, with no shutdown happening.

The only quirk is that if power comes back on *after* the shutdown has begun, the UPS will still wait one minute and power itself off, even though it starts right back up a second later. Not sure if this is a software or hardware issue, though.

My only potential complaint is that I've seen a bit of instability after installing this, though I'm not sure it's APC's fault (applications have a couple of times acted as if they're open, but weren't actually running--this prevents force quitting them and restarting them, and makes it impossible to logout without killing your loginwindow process).