From my point, PowerShell is not a good product.

Shell, by definition, is something that glue the applications together. In the Unix world, if you follow the basic conventions, like deal with stdin, stdout, stderr, everything is string, exit code 0 stands for success ..., then you are OK. It doesn't matter whatever language, whatever library you are using. It will be very easy for the end users to call your code. And if other people also follow the same convention, it should be equally easy for you to call their code. However, PowerShell is totally different. Everything is .NET. The arguments, the return values, and even the invocation of the PowerShell commands are .NET stuff. So if you want to write some code that needs to talk with PowerShell, and the language or the library are not .NET ready, then you are screwed. In this way, Powershell is not a shell for the operating system, it is just a shell for .NET.

But MS has really done a great job. PS actually is pretty handy by its own. But the problem is, shell is not a something that mean to play by its own.