I can see where Powershell would be incredibly useful for a system administrator and/or, perhaps, a DBA, but I'm neither a system administrator nor a DBA and I haven't found that many cases where it would seem an attractive adjunct to anything I'm doing. As a result, when I do find myself in a situation where I think it would help, I can't remember any of the syntax, etc., and need to spend more time refreshing my knowledge than it would take to just go do whatever it is I'd hoped to script out. Part of the reason that its utility seems to be limited is that, like most scripting languages, it works best when the tools it is interacting with were designed to work with it. Being able to access a tool's object model directly is great if the object model is exposed and was designed with an eye towards automation, but most were not. The reason Unix's scripting languages became so popular is that most of the tools in the operating system were designed from day 1 to work in a pipeline so a scripting language that can manipulate pipelines was pretty much guaranteed to get used.
IBM introduced a scripting language called REXX for their mainframe systems (back in the 70's or 80's if memory serves). It took a different approach and required a tool to include a portal which REXX could link up to -- once linked it could manipulate the tool through any commands exposed by that portal. I never used REXX on a mainframe but the language was adopted as the official scripting language of the Amiga computer (dubbed ARexx) and I used it fairly extensively there. It had similar issues to those of Powershell. Tool vendors who added portals with powerful automation commands allowed manipulation by ARexx to do some truly impressive things. Many tools either never implemented portals or did so in a manner which was ill-conceived or simply thrown together so they could advertise support (consider a word processor which allowed one to automate entry and editing of text but without allowing for determining what files were open, where the cursor was positioned or even to read the text in the file). The more support tools have for automation the more impressive will be the uses we will see in Powershell and perhaps at some point I will find it useful enough to learn it and remember it. I wouldn't hold my breath waiting for widespread support, however -- as I recall, when Microsoft introduced the concept of drag and drop in windows, many of Microsoft's tools were the last to implement the concept.