Just another note, one of the developers/maintainers of apcupsd, Kern Sibbald is probably one of the nicest guys I've had the pleasure to interact with, he is extremely helpful, and patient. If you have questions, his list (which he answers almost all the questions) is a great resource.
Just my experience, for me, it's people like him that make Open Source software such a pleasure to use.
If you have an apc ups you can't go wrong with apcupsd.