I had an APC brand UPS that finally died. Ran for almost 10 years so I'm not complaining.
What DID bother me was replacing the damn battery. They never put any kind of model number on the stupid thing so figuring out which one I needed was a pain. At the very least they could have labelled current and voltage ratings so I could figure out what the replacement MIGHT be.
I don't remember having that problem with my APC unit (wife's computer). I went to CyberPower's website and I got the info with a little digging. I almost just bought the whole battery pack, but I replaced the batteries on my identical UPS for my main rig back in February and just reused the harness that connected the two batteries. Figured I'd just do it again.
What's funny is that the APC original batteries leaked. Notice that the CyberPower label says NONSPILLABLE. I thought that might kill the APC unit. I just wiped up the battery acid, cleaned it well, let it dry and then replaced the battery pack. Worked. Better than buying a whole new unit. These PFC 1000VA+ UPS units are expensive.