It is hard to find the PowerShell 3.0 download. That is because the only way to get it is to download the Windows Management Framework 3.0. PowerShell 3.0 is part of that.
Windows Management Framework 3.0http://www.microsoft.com/en-us/download/details.aspx?id=34595
Ok, now that you know where to get it what value does it bring? You can install the download on Windows 7, Server 2008, and Server 2008 R2. It gives you the speed improvements in PowerShell as well as the new command-lets.
One of the things I like about it is that I can use the new Server Manager tool to manage Server 2008, 2008R2, and 2012 boxes. You do need to load this on your 2008 and 2008R2 boxes to get that to work.