Also, most of the APC products (all?) come with software (PowerChute I think) that will tell you what the status of it is. It totally depends on how much you have plugged in. You can have the machine automatically shut down when you reach, e.g., 10% of capacity, so if you're not home, but it's running, you'll be protected.
I have APC products for everything, and I've been generally satisfied. The only problem is during an extended power outage they keep beeping, which is a bit annoying. But I have one even on my home entertainment center, esp. for the Tivo, but also for the other components. I don't need it to last forever, but it helps for the those 30 sec.-2 min. blackouts, so I don't have to reset the clocks.