I opted for a unit from CyberPower because it said that it supported Mac and was $30 cheaper than a comparable model from APC. I've always gone with APC and Tripp-Lite for my customers because, frankly, I don't know and trust CyberPower like I do the the other two. But $30 is enough to convince me to try it, and it's my own computer, so noone but me will be aggravated when it breaks. Hopefully I'm in for a pleasant surprise and the unit will be higher quality that I anticipated.
I plugged in the new unit (CyberPower 850VA model CP850AVRLCD), plugged in all my cords and wall warts (Linux box and iMac on the battery side, router, switch, and WAP on the surge only side), plugged it in, hooked up the USB cord to my iMac, and was pretty much done. Surprisingly enough, OS X comes with built-in UPS management software that is under Apple -> System Preferences -> Energy Saver -> UPS tab.
Your computer will now go to sleep with the RAM contents saved after it has been on battery for the time you set. If the battery runs out of juice the computer goes off. When power is restored the computer comes back on. Hopefully the power remains on for a while and allows the battery to recharge because too soon a repeat outage and your sleep timeout won't be reached before it's cut off.