It might seem that investment into UPS is a big deal.. as far as you lost a data after power outage.
Yesterday I was in such situatation. Outage of power was only for 1-2 seconds, but it was enough to my PC. It turned off and after I turned it on again, BIOS was not able to detect my hard drives. I've got 2 drives on my PC, but none of them is detected.
I've completed no fine diagnosis yet, and still hope that hard drives are OK or at least, I could restore something. Fortunately, last times I more use my notebook for work, so all latest information is there. On a PC I've got my all my old projects (with local SVN server, no backed up some service) a lot of books, photos and music. Photos would be the most painful thing to loose.
You always can hear about importance of backup but does not take it seriously as soon it does not happen to you. It happened to me and now I feel not so great. For now I'm thinking of how to minimize or avoid such in future. For sure, spending about 200 bucks for UPS doesn't sound bad idea now. I would also finally buy additional space on google to store all photos in picassa with original size, so you will always have a backup. All important projects, documents other artifacts, should be on copied on services (Google Docs, Google Code, github etc.). Music, videos and so on is backed up for external USB hard drive. Now, it is not so expensive.. and there is a chance that this hard drive could also be corrupted, but it is better than nothing.