We don't have a unified UPS. All our servers have dual power supplies so we have a dedicated 1U UPS plugged into each power supply (so two UPSes per server). We've been an APC shop for the past 15 years so they're currently they're APC Smart-UPS 1000 RM 1U units.
However, getting Powerchute to work with our old ESX 4.1 environment was a huge pain, and it doesn't look like it's gotten much easier since.
I'm currently standing up a new ESXi 5.5U3 environment and I'm buying new UPSes for it. As such I'm looking at the Eaton 5P1500R 1U UPS with the added network management modules since the Eaton IPM software seems to integrate very nicely with ESXi and vCenter.
It seems Eaton has a good reputation and I hear they don't make their batteries swell up (which all of my APC units have always done).
Any reason for me NOT to pull the trigger...