I ordered one of the silver S15 units from Vann's in January of this year. It arrived nonfunctional. Battery may have been dead, and there may have been some fairly large internal object that had broken loose. If I turned the unit on its side, I could hear some large object rolling around inside. Vann's offered to take it back, but I called APC and described the situation. Based on the serial number, they told me the unit was actually about 5 years old (it was not previously used -- probably had been sitting around somewhere for 5 years). They were originally just going to send me a new battery, but after I described the sound of something loose inside, they decided to send me a new unit. So I returned the nonfunctional unit to APC and they sent me a new (black) S15. No charge from APC for any of this. So APC backs up its products. I have been using this new unit since late January with no problems. Silent during normal operation. It does seem to detect power fluctuations as I occasionally get a message that I am running on backup power. Then the fan comes on. These happen briefly and very transiently, and I just click OK on the message to make it go away. I think it may be a sensitivity issue -- this can be adjusted between high, medium and low sensitivity. I haven't bothered to adjust it yet.
In summary, now that I have a working S15 I am happy with it. The price was low, I had some minor inconvenience, but all now seems well.
