I fail to realize why any of these features were "important problems" of Unix shells. Passing byte streams between programs is a very powerful idea and transfers the responsibility of interpreting what the input is to the program parsing it. I realize, from a programmatic point of view, that being able to get a series of objects and to invoke a specific method on them is an intriguing idea, but it breaks the simplicity of the Unix approach of each utility doing one thing and doing it well.
The tight integration into the OS is another weakness - I can grab my Linux scripts and run them on OSX, BSD, AIX, Solaris and pretty much every Unix-like OS around. Your PowerShell scripts will never run on anything other than Windows.
a) I fail to realize why any of these features were "important problems" of Unix shells.
b) Passing byte streams between programs is a very powerful idea and transfers the responsibility of interpreting what the input is to the program parsing it.
b) is an important problem. It means that there are zillions of implementations of various parsers. That inefficiency costs money. Worse, not all of them are without bugs. For an example consider the problem of searching by file name in a script. I guesstimate that a large proportion of Linux installations has a buggy version of it somewhere. Doing it reliably (file names can have spaces, may contain control characters or slashes) involves, IIRC, setting $IFS.
> It means that there are zillions of implementations of various parsers. That inefficiency costs money.
Most of them (if you are referring to command-line utilities) are open-source. I see this variety of implementations as a good thing - evolution relies on diversity and the openness makes it possible for software to "reproduce sexually", making evolution easier.
The tight integration into the OS is another weakness - I can grab my Linux scripts and run them on OSX, BSD, AIX, Solaris and pretty much every Unix-like OS around. Your PowerShell scripts will never run on anything other than Windows.