Took me a minute to realize why you wrote out "uninterruptible power supply" - not sure why I wrote universal, I'll have to edit that.
I live in the boonies, so power can be iffie. I'll be honest, my biggest concern is actually the occasional firmware upgrades. My home theatre room is relatively cool, so the projector rarely needs to cool down for any longer than it takes to shut down so that's not a big concern for me. That being said, the PS3 does have a HDD and I've run into issues with it "not shutting down properly" in the past - it's never caused any HDD problems, but I'd prefer not to take that chance.
So, I'll restate my question now that I've provided a bit more information. Are there any recommendations given my situation? As I said, reliable power is a problem and small outages are frequent. The UPS would likely only be needed a few minutes, but to be safe I'd like to be capable of running off it up to about 15 minutes.