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.