A python based PowerShell?
I've only dabbled in Powershell, but what distinguishes it for me is the ability to pipe actual objects in the shell. In that respect, the closest I've found is actually using the IPython shell with ipipe:
Following the recipes shown on that page and cooking up my own extensions, I don't often leave the IPython shell for bash. YMMV.
I think Hotwire is basically what you're thinking of:
http://code.google.com/p/hotwire-shell/wiki/GettingStarted0700
It's a shell-type environment where you can access the outputs as Python objects.
It doesn't have all PowerShell's handy hooks into various Windows system information, though. For that, you may want to literally integrate Python with PowerShell; that's described in IronPython In Action.