I think it is essential for hard drive recorders (PCs, DVRs, etc.) and to protect projection lamp displays.
For other equipment it does fine for regular protection, but only the topline UPS put out a pure sine wave.
It is not a good idea to daisy-chain separate power protection and back-ups. They can have totally
different load requirements and react adversely during outages, brown-outs, etc.
I would not use an UPS for equipment that has high power demands, like power amps.
There's excellent surge protection for those made by Panamax, Furman, Zero Surge, etc.