Check out the amazing PowerShellIDE at http://PowerShell.com .   Many of you probably already know Dr Tobias Weltner from his product SystemScripter http://www.scriptinternals.com.  The PowerShell team has been talking to Tobias on and off for years now and those discussions have clearly paid off.  PowerShellIDE is a free "experimental editor" whose functions will be integrated into SystemScripter. 
The things that I really like are the rich intellisense, rich syntax coloring, rich inspection capabilities, and rich debugging that PowerShellIDE brings to the table.  Did I mention that it was RICH?  Check it out yourself and you'll see exactly what I mean.  This tool can really accelerate learning and scripting PowerShell.