It doesn't copy all the good things about the Unix shell though.

The reason people are comfortable with the POSIX shell is because you use the same syntax for typing commands manually as you do for scripts. But, you're going to have a hard time finding people who prefers writing:

    Remove-Item some/directory -recursive

Rather than

    rm -fr some/directory

People who write shellscripts are often not seeing themselves writing a "program". They are just automating things they would do manually. Going to an IDE in this case is not something you'd consider.

I happen to be very aware of all the pitfalls in POSIX shell, and it's rare that I see a shellscript where I cannot immediately point out multiple potential problems, and I definitely agree that most scripts should probably be written in a language that doesn't contain so many guns aimed at the user's feet. I'm just pointing out a likely reason why people are not adopting powershell in the huge numbers that Microsoft may have hoped for.