|i have a tripp-lite internet office 500. i use nut (which is REALLY easy to config as the config files are thoroughly commented) and the combo works. i can't really say whether it works "good" or "great" because this is my only experience with an ups, so i have nothing to compare it to. but i can say that it works.
the ups is a "dumb" ups in that it only provides status. it is equivalent to an apc back-ups, in that both are "dumb" ups. it simply reports wether the ups is on or off, and whether the ups is on ac or battery. you (and any software) can assume if the ups is on battery, then the ac power is off.
nut does do some reporting through a cgi, but i'm not interested in viewing my ups status from afar. nut has always accurately reported to syslog when the power goes on or off (actually, when the ups switches between ac and battery), so it "monitors" the ups great for my use.
my tripplite initially did over 20 minutes (that's when the low battery warning came on and i didn't want to push the test any further as i only need to know when to set the shutdown sequence timer in the software), but i messed around with red hat's anaconda hardware detection app (DON'T DO ACTIVE/AGGRESSIVE SERIAL PORT PROBING WITH THE UPS ATTACHED) and somehow that confused the ups and caused it to overcharge the battery. i now get 12 minutes until the low battery warning. i don't know how much of that decrease is due to my accident, eventual breaking-in of the battery, or what.
take the apc and tripplite power estimators with a grain of salt. i was told to get a >= 700VA ups based on my system and i would have a 10 minute up-time, but instead i run that same system (PII 450MHz, 15" monitor) and another (486 66MHz, headless) and get 12 minutes (initially 19 minutes) which is more than what they said i would with the one system on a larger ups. i think the estimators produce over-inflated numbers.
one big disclaimer: i have never used nut to automatically shutdown my system. i have never needed to as the power was never out longer than 10 minutes. i think i remember that nut simply executes whatever command you tell it to, so a simply "shutdown -r now" should work.
i do have two systems connected to the ups, so i run the nut "server" on the machine whose serial port is connected to the ups, and the client on both machines, so both machines know when power goes off and can auto-shutdown.
if you just want an ups that helps carry you through intermittent black-outs (five or six in the last year, never lasting longer than 10 minutes) with the capability to autoshutdown and don't care about a fancy gui but instead just something that runs in the background consuming few resources, then i can recommend a "dumb" tripplite with nut setup.
1. there's other ups-monitoring software out there that performs the same function as nut (one even has an ssl version in non-us for encrypting server-client communication), but i learned of nut first, liked the (unix) design philosopy of nut, and became familiar with it.
2. i chose tripplite instead of apc because of price. for a va-rated comparable ups, tripplites are cheaper. my ups was $110. a comparable apc was $150. i will admit that the apc is better/smoother/flashier looking, but from my research on groups.google.com, customers were just as pleased/displeased with both. i did find a REALLY good deal on an apc ubs ups, but a year ago linux-usb did not support apc upses and no ups-monitoring software could verify that they worked with a usb ups.