This is probably true, if you're mostly only going to work in Windows. But if you're going to work in *nix and Windows, your bash/cygwin skills/experience will

This is probably true, if you're mostly only going to work in Windows. But if you're going to work in *nix and Windows, your bash/cygwin skills/experience will be useful in both locations, and much of your work will be reusable between the two worlds. Powershell is Windows-only, which is fine if your life is Windows-only or Windows-heavy. Not that there's anything wrong with knowing and using Powershell.