This isn't pointed at you, keyle, but here PowerShell seems to be one of those things that's universally panned by people who don't understand it, or who refuse to give a serious chance to anything that isn't a traditional Unix shell...

To answer your question, PowerShell's big win is that it's an object-oriented shell on top of .NET. Where the Unix shell pipes flat data, PowerShell pipes .NET (and COM) objects.

In practice this means things that may require complicated and often fragile text-wrangling in the Unix shell are straightforward and robust in PowerShell. For example, suppose you wanted to kill all processes with a private working set greater than 1 GB:

    ps | ?{ $_.PM -gt 1GB } | %{ $_.Kill() }

Here ps returns a collection of all current processes, then pipes it to the where-object cmdlet (abbreviated "?") which filters the collection to those with a private working set greater than the given size. The filtered collection is then piped into the foreach-object cmdlet ("%") which invokes the Kill() method on each object passed in – these are real .NET objects being passed around, so you can invoke methods, set properties, etc.

You can get the same result with a Unix shell script, but you have to be careful to count the columns output by ps correctly, skip the output header, pass it through awk, save the corresponding PIDs and then invoke the kill command on them... and then it all breaks if you run it on a different Unix system where ps outputs a different formatting. In practice you usually leave the shell environment and write a Perl or Python script instead for this sort of thing.

In PowerShell you can directly instantiate .NET and COM objects, and you can implement your own cmdlets and modules either in the PowerShell scripting language or in any .NET language like C# or F#. So e.g. you can access the .NET class libraries to get the time as so:

    [System.DateTime]::Now

And this makes PowerShell handy for interactively developing .NET class libraries (at least until C# gets a real REPL, and if you aren't using F# anyway). Of course this object-oriented approach is all the more necessary on Windows, which is inherently an object-oriented system (think OLE automation, WMI, etc., let alone .NET) than it is on Unix-based systems.

Some people will complain about the PowerShell scripting language... and sure, it's not perfect, but I think the team did about as good a job as possible satisfying the various requirements involved in building a new Windows shell language that could be used both interactively and as the basis for writing scripts. Superficially the language is heavily influenced by Perl, and while I'd still rather use Perl for "serious" automation tasks, PowerShell gets the job done... and it's nowhere near as ugly as scripting in the traditional Unix shell, nevermind the old Windows command shell.

For more on the design rationale, in the words of one of PowerShell's creators:

http://stackoverflow.com/questions/573623/powershell-vs-unix...