Not sure if the community is aware yet, but the latest version of APC PCNS, v3.0.0 is now free. Albeit you need to have a supported Management Card installed in the UPS to use it. It has a release date of 19may2011.
Setting up ESXi 5.1 with an APC SmartUPS connected through USB Disclaimer: I’ve used these steps to connect an APC Smart-UPS 750. I have no reason to believe it wouldn’t work in other setups, but I can’t confirm. VMware vSphere Plug-in Options. A vSphere plug-in option integrates PowerChute with vCenter Server for ease of management enabling PowerChute monitoring with the vSphere Client. Plug-in options are available for either the vSphere Web Client or vSphere Desktop Client. 2019, APC by Schneider Electric.
I already had v2.4.4 installed on a ESX 4.1 box and it ran without issues and did shutdown the guests when your configuration in VMware is correct.
The upgrade procedure went smoothly and I didn't loose any of my previous settings.
There is a cavet, as the version of Java has changed. The release notes say to remove the old version of java before doing a update or the new version of java won't be installed. I just stopped the PowerChute Service, renamed the folder for the jre installed, then ran install script for PCNS 3. It detected the previous version of PCNS and updated everything and installed the new version of java.
You can grab PCNS v3 here http://www.apc.com/tools/download/software_comp.cfm?sw_sku=SFPCNS300&id=127&family=127&part_num=SFPCNS300&swfam=&tsk=