I have issues with the APC brand of UPSes, some RFI-related issues and others that are not RFI-related.
My house is full of running UPSes courtesy of a buddy of mine that has a small battery recycling depot. He absolutely hates disassembling things to get the batteries out so we have an arrangement where I remove the batteries for him and I can keep whatever it was that the batteries were in, whether it's a UPS, those 12V booster box / inverter things, an old office PBX or whatever. It's amazing (and kind of disgusting) how many people and businesses throw out perfectly good devices because the battery has gone bad.
A whole pile of APC ES350 UPSes came in a few years ago so I installed new batteries and put them into service at my home. "ES350" is a pretty useless designation, you need to get the full number off of the product sticker on the back as these "ES350" UPSes are different shapes, sizes and take different batteries. There is a UPS running in every room of my home now and two or more in my living room and basement. While they are reasonably RF-quiet I have one that is a pest on 40M from time to time, weeks can go by and then it starts its raspy wandering across the band. If I unplug it, let it kick over to its battery and then plug it in again it will clear the RFI. I could never understand what sets it off as there's no difference from day to day in the UPS's use or application.
One issue I have with with APC is the line frequency, it is only vaguely related to 60 Hz. One of my intentions in installing UPSes all over the house was to keep my clocks running so I don't have to run all over the place setting the time after a power interruption. It didn't work out that way. After anything more than five minutes or so of UPS running time any relation to the actual time and what the clocks that use the 60Hz line frequency for timing are displaying is just a coincidence, so I end up having to set them anyway. Whereas these UPSes run on a crystal time base it's probably poor quality crystals not close enough to the required frequency, just like those cheap wristwatches.
My main beef with APC is their programmed running time that is completely unrelated to the state of the battery. This REALLY vexes me and is why I would never buy one of their units although I fully expect that other manufacturers are doing the same thing. My expectation with a UPS is that it will run until the battery drops to a certain level and will then shut off, giving you as much running time as possible in an emergency. Not these ES350s. They shut down after a pre-programmed time whether the battery is still good or not, I've run tests on multiple units. This is also where the product ID rather than the model number comes in. Certain ES350 units I have, all with the same product code, will give about 45 minutes more-or-less. Each specific unit varies a little bit but they all shut down within a minute or two of each other. Cycle them (reset the UPSes by plugging them in and immediately unplug them again) and they will continue to power the test load (light bulb or whatever) for another cycle even though they had just shut down. I can do this several times before the batteries finally die, depending on what I'm using for a test load, of course. Other ES350s I have with different product codes will give a different running times. I've looked up these product codes on their web site and the longer-running units are of course the more expensive ones. So keep in mind that they're selling you running time not just watts.
I've retrofitted all of my units with those common 6" x 3.5" x 2.5" gell cells used for emergency lighting in buildings, fire alarm panels, etc, rather than purchase APC's unique replacement batteries. That gives me extra capacity, too bad they won't let me use it. Since my units are salvage and well out of warranty I've also modified them by disabling the sounding device and installing a green LED across the coil of the relay that drops when the UPS kicks in during a power outage. All of the above-mentioned tests and evaluations were done on unmodified units. The green LED gives me an indication of AC power and when the power goes out I don't have to sit there in the dark listening to peeep... peeep... peeep... peeep...