UPS systems are nice, but they are dreadfully inefficient for a product which needs every precious second of time. However, note the conversions:
AC wall -> DC battery -> AC UPS -> DC power supply.
Why can't I get a UPS that converts the power to DC, stores it in a battery, and delivers the power to a 12v (power supply/regulator/splitter) without converting. Firstly, this will stop a bunch of worthless conversions of the power current, this will replace a power supply with a simple box which splits and regulates the power flow that won't need fans and other such things.
Also, this would allow for pretty quick easy server rack, multi-power supply. It turns out you can save a ton of power if you have one large power supply to serve a large rack of computers. This would do roughly the same thing but add UPS.
Worst case a few super capacitors could one day be put into the power supply after the conversion of DC power and provide some nice functionality. That or just convert all the computer's memory to non-volatile.