I suppose if I sat down and started learning how to become a brain surgeon (being a software developer), 20 or 30 hours of studying would get me as far as 2+2 is in math. Hardly competent enough to do anything as a surgeon. But, going through some new technology built on an existing one that I am very familiar with already (ie: familiar with .NET and C# and MVC and now attempting to learn WebAPI, or knowing MSTest unit testing framework and now attempting learn TSQLT) then 20 or 30 hours can really be productive.

Same would go for the PowerShell Challenge you speak of. If you've programmed in several different languages already then 20 or 30 hours of PowerShell studying can get you going on a pretty high scale. If you have never heard of "command line" and never seen a single line of code before in your life, 20/30 hours of studying PowerShell will definitely not qualify you as an expert.