I do feel you missed a whole chunk of info out of the UPS podcast. In particular that OSX can integrate with systems with USB and not only give the status of the UPS in the menu bar but also auto shut down when power is low. Surely this is the reason to have one UPS per computer?
The extra tab in the power settings that appears allows you to choose when this happens both in terms of time and % battery
The above info relates to APC systems with USB but there may be others as well. No extra driver needs installing – it just works!
— Crispin Hodges