Powershell exposes extremely complex internal Microsoft Windows-specific data structures to simple manipulation, and potentially preserves your scripts' ability to manipulate those structures across operating system patches and upgrades. For example, you can change the name of a user object without having to understand the underlying kerberized LDAP data transport of AD or the actual layout of the local user data block. It absolutely rocks for simplifying system programming on Windows.
Other than that, it's just a scripting language, nothing special. You might like the syntax more than an older, heavily accreted language like Bourne Shell, but that's just a matter of taste and familiarity really. Personally I have no trouble writing code in it, and I like Snover, he's a very bright guy who seems to have a good heart.
Having it available on non-Windows systems is of limited utility, since linux and Mac systems don't have the Windows internal guts that Powershell is so excellent for working with. But, remember future high performance windows servers are intended to be GUI-less, stripped down kernels like Nanoserver with all management performed by remote Powershell, so this will be great for systems integration in that environment.