Is PowerShell ready to replace my Cygwin shell on Windows?
grep
Select-String cmdlet and -match operator work with regexes. Also you can directly make use of .NET's regex support for more advanced functionality.
sort
Sort-Object is more powerful (than I remember *nix's sort). Allowing multi-level sorting on arbitrary expressions. Here PowerShell's maintenance of underlying type helps; e.g. a DateTime property will be sorted as a DateTime without having to ensure formatting into a sortable format.
uniq
Select-Object -Unique
Perl (how close does PowerShell come to Perl capabilities?)
In terms of Perl's breadth of domain specific support libraries: nowhere close (yet).
For general programming, PowerShell is certainly more cohesive and consistent, and easier to extend. The one gap for text munging is something equivalent to Perl's .. operator.
AWK
It has been long enough since using AWK (must be >18 years, since later I just used Perl), so can't really comment.
sed
[See above]
file (the command that gives file information)
PowerShell's strength here isn't so much of what it can do with filesystem objects (and it gets full information here, dir returns FileInfo or FolderInfo objects as appropriate) is that is the whole provider model.
You can treat the registry, certificate store, SQL Server, Internet Explorer's RSS cache, etc. as an object space navigable by the same cmdlets as the filesystem.
PowerShell is definitely the way forward on Windows. Microsoft has made it part of their requirements for future non-home products. Hence rich support in Exchange, support in SQL Server. This is only going to expand.
A recent example of this is the TFS PowerToys. Many TFS client operations are done without having to startup tf.exe each time (which requires a new TFS server connection, etc.) and is notably easier to then further process the data. As well as allowing wide access to the whole TFS client API to a greater detail than exposed in either Team Explorer of TF.exe.
Tools are just tools.
They help or they don't.
You need help or you don't.
If you know Unix and those tools do what you need them to do on Windows - then you are a happy guy and there is no need to learn PowerShell (unless you want to explore).
My original intent was to include a set of Unix tools in Windows and be done with it (a number of us on the team have deep Unix backgrounds and a healthy dose of respect for that community.)
What I found was that this didn't really help much. The reason for that is that AWK/grep/sed don't work against COM, WMI, ADSI, the Registry, the certificate store, etc., etc.
In other words, UNIX is an entire ecosystem self-tuned around text files. As such, text processing tools are effectively management tools. Windows is a completely different ecosystem self-tuned around APIs and Objects. That's why we invented PowerShell.
What I think you'll find is that there will be lots of occasions when text-processing won't get you what you want on Windows. At that point, you'll want to pick up PowerShell. NOTE - it is not an all or nothing deal. Within PowerShell, you can call out to your Unix tools (and use their text process or PowerShell's text processing). Also you can call PowerShell from your Unix tools and get text.
Again - there is no religion here - our focus is on giving you the tools you need to succeed. That is why we are so passionate about feedback. Let us know where we are falling down on the job or where you don't have a tool you need and we'll put it on the list and get to it.
In all honesty, we are digging ourselves out of a 30-year-hole, so it is going to take a while. That said, if you pick up the beta of Windows Server 2008 /R2 and/or the betas of our server products, I think you'll be shocked at how quickly that hole is getting filled.
With regard to usage - we've had > 3.5 million downloads to date. That does not include the people using it in Windows Server 2008, because it is included as an optional component and does not need a download.
V2 will ship in all versions of Windows. It will be on-by-default for all editions except Server core where it is an optional component. Shortly after Windows 7/Windows Server 2008 R2 ships, we'll make V2 available on all platforms, Windows XP and above. In other words - your investment in learning will be applicable to a very large number of machines/environments.
One last comment. If/when you start to learn PowerShell, I think you'll be pretty happy. Much of the design is heavily influenced by our Unix backgrounds, so while we are quite different, you'll pick it up very quickly (after you get over cussing that it isn't Unix :-) ).
We know that people have a very limited budget for learning - that is why we are super hard-core about consistency. You are going to learn something, and then you'll use it over and over and over again.
Experiment! Enjoy! Engage!