In my (rarely humble) opinion, Powershell proficiency is a skill any DBA working with Windows-based servers should acquire. If you have any task that would benefit from automation, it can almost certainly be scripted using Powershell -- Powershell does more than just fill the shell-scripting gap left by Microsoft's abandonment of VBScript, it is as clear an improvement over VBScript as VBScript was over command-shell batch language.

As just one example, I am steadily replacing SSIS packages with Powershell scripts for improved maintainability. Between being able to actually read the logic in a single interface and having much clearer debugging, working with .dstx files in a Visual Studio plug-in seems positively painful in comparison.

For another example, I'm able to use Powershell to automatically synchronize the contents of several file structures on geographically dispersed servers with minimal effort (roughly 3 dozen lines of very readable Powershell code does the trick). And I'm just getting started finding production uses for Powershell.