PowerShell is interesting, but seems like a classic Microsoft solution.
By which I mean that Microsoft has some fantastic developers, some great minds - but they work in a very monolithic way. They set out their paradigm (ugh, I feel dirty for using that word even when it's appropriate!) and they stick to it.
So when I'm using PowerShell to administer a Windows environment, it's great. It works really well. For example, the other day I wanted to get statistics for some Exchange mailboxes. With a few pipes of mailbox objects into Where-Object for filtering, and a bit of sorting, and finally outputting to ft, I had a nice little report.
But the reason that the word paradigm is validly used is that the moment you leave their use cases, you're screwed. PowerShell is a very nice walled garden for administering Microsoft products, but for doing anything outside of that it's pretty poor. (So for example if the statistics I wanted aren't served by their cmdlets/objects, I'm straight back to writing a program rather than a script for it.)
This is why I keep UnxUtils - a Win32 port of essential GNU utilities - on my machine at work. Whilst I administer no *NIX boxes at all in my job, and am technically not a *NIX administrator or even close, having grep/sed/awk saves the day a lot more often than PowerShell ever does.
PowerShell is great for day to day admin of the Windows-based products, but the moment I find myself with a non-Microsoft logfile or similar, PowerShell is no longer the solution.
By comparison, the other day I solved an issue with reporting via a (slightly convoluted) chain of grep->awk->sed->tr. The issue was getting statistics from "XML" report files that a process dumps when it's completed. My other options were to write an actual program using an XML library and VBscript/C#/$whatever.
Or to chain together 30 year old UNIX tools to create a CSV file from (slightly dodgy) XML.
I tell no lie when I say that it took me longer to convince Excel 2010 to produce a usable chart from the data after importing than it did to extract the raw data. It was under two hours to get the data out, and a lot longer struggling with Excel's poor interface for multi-axis charting....
And I'm not a UNIX expert - I had to refer to the O'Reilly sed/awk manual several times.
So in a nutshell, PowerShell is a great environment - but it's designed by programmers for one specific environment, and doesn't work at all once you leave their specifications. By contrast, the UNIX utilities are so broad and useful that people are still applying them to uses that the authors probably never even imagined would be possible, let alone probable.
I'd like a PowerShell style UNIX environment, but I suspect I'd still end up calling grep/sed/awk many times within it precisely because an object isn't going to be as useful as I'd like at that point in time.
This isn't to say that PowerShell isn't very powerful and nice - just to say that until it gets a decent set of tools that allow it to step outside its own paradigm and just work with anything it's given, it will always be a walled garden.
(Albeit a garden of national park proportions.)