Pros: Solid build quality, seems to consistently power my PC and monitor.

Cons: As soon as I received the backup, I connected the internal battery as directed by the instructions, plugged it into the wall and I immediately noticed a very high pitch noise from the UPS. The noise is the kind of barely-audible high frequency pitch that sounds like the feedback from a hearing aid. The sound was not a single frequency, but whistled a little and I was actually concerned it might blow up or melt down. I tried to ignore it, assuming the sound was due to an unusually high current draw while the internal battery charged up from brand new so I let it run while I was assembling the computer that would be plugged into it. After an hour the sound had not decreased in volume so I turned on the UPS and the LCD indicated the battery was fully charged. At this point I started becoming concerned. I had already gotten a slight headache from the persistent high pitch sound and was not feeling comfortable about this purchase. I kept it plugged in over night, hoping that a break-in period might reduce the sound. After checking this morning it was still as loud as before and I'm not happy. I purposely spec'd my computer to be very quiet. My computer room has very low ambient noise so this UPS is noticeably the loudest thing in the room.

Overall Review: The APC website lists the ambient noise generated by this UPS to be 45 dBa at 1m. This could be accurate, and it could simply be caused by current flowing through the transformer. However, not reading any similar comments in any other reviews makes me think that I either have a defective unit or this is normal for UPS devices. Full disclosure: I'm a guy that can hear if a TV monitor is powered on and I regularly unplug my cell phone usb adapter from the wall because it makes a similar high pitch noise that keeps me up at night since it's right next to my bed. I may be unusually sensitive to high frequency sounds like this.