Considering how hot and crowded virtualization space is, it is just amazing that PowerGUI (combined with PowerCLI and Community PowerPack) is number one among the free tools in this space!
See the Top 10 Free VMware vSphere Tools and Utilities for 2011 lists here, and let me quote the PowerGUI entry for you:
This set of free tools ranked number 1 on last years free tool list and it’s not going anywhere anytime soon. When you combine these three products together it becomes Voltron. Yes, I just used a Voltron reference! These three products bring with them a set of tools that can’t be found in anything else. PowerCLI is the framework that makes it all possible. PowerGUI is the interface that enables anyone from a beginner to advanced user to become proficient. The PowerPack is the secret sauce that brings added functionality to every vSphere admin. Quest is currently working on updates for vSphere 5, but most of the functionality was there with the PowerCLI vSphere 5 beta I had been testing. Try it out and you will know why this tool continues to be on the Top 10 list.