I took a slightly different route. After a few basic HowTo exercises from the Web I worked my way through "Windows PowerShell in Action" and found it very enjoyable. Of course I do not remember everything (far from it!) but it was a great way to get a general feel for the language and some idea of why things are the way they are. I still use it as my main reference book.

I am currently reading "PowerShell Toolmaking in a month of lunches", mostly in the weekends. It provides a refreshing perspective on scripting and I have picked up a lot of useful things - not so much syntax but ways to organise my scripts. I don't care for the "lunches" thing at all though; for me an hour here and there does not work because it wastes too much time getting back to where I left off and anyway I need more than an hour in one go to properly experiment with a new idea.

I believe the topics you need to study depend somewhat on the job you're doing. For example I am not a domain admin and so far I have not needed to use remoting at all. But I often need to write scripts to automate scheduled interaction with Active Directory, SQL Server and the file system, and I am fanatic about logging script progress and capturing all errors. Compared to CMD scripting PowerShell wins hands down.