I have an APC XS 1500VA unit that just finally failed on me (batteries crapping out). It's been quite useful, but power here has been less-than-good, mostly due to me tripping out a breaker roughly ...
I have a (refurbished) APC Back-UPS LS 500 I've been using for a year and a half or so, and recently when the power's been crappy (thanks to bad drivers...) I've noticed it's no longer doing the thing ...