To quote the completely understated download blurb:

Windows PowerShell V2 CTP3 introduces several significant features to Windows PowerShell 1.0 and Windows PowerShell V2 CTPs that extends its use, improves its usability, and allows you to control and manage the Windows environment more easily and comprehensively.

The release notes are quite extensive. Here is the section on breaking changes from CTP2:

Breaking Changes to Windows PowerShell V2 (CTP2)

The following changes in Windows PowerShell V2.0 CTP3 might prevent features designed for Windows PowerShell 2.0 CTP2 from working correctly.

• Following cmdlets have been renamed
  • Add-Module to Import-Module
  • Get-Event to Get-WinEvent
  • *-Runspace to *-PSSession
  • Push-Runspace to Enter-PSSession
  • Pop-Runspace to Exit-PSSession
  • *-PSEvent to *-Event
  • Register-PSEvent to Register-EngineEvent
  • *-PSTransaction to *-Transaction
  • *-PSJob to *-Job
  • *-PSEventSubscriber to *-EventSubscriber
  • *-Bite to *-FileTransfer

• Following parameters have been renamed
  • Import-LocalizedData: Culture to UICulture
  • Invoke-Command: Runspace to Session, Shell to ConfigurationName
  • Get-Job: SessionId to Id
  • Receive-Job: Runspace to Session, SessionId to Id
  • Remove-Job: SessionId to Id
  • Start-Job: Command to Scriptblock
  • Stop-Job: SessionId to Id
  • Wait-Job: SessionId to Id
  • Get-PSSession: RemoteRunspaceID to InstanceId, SessionId to Id
  • New-PSSession: Runspace to Session, Shell to ConfigurationName
  • Enter-PSSession: Runspace to Session, RemoteRunspaceID to InstanceId, SessionId to Id, Shell to ConfigurationName
  • Remove-PSSession: Runspace to Session, RemoteRunspaceID to InstanceId, SessionId to Id

• Following parameters have been deleted
  • Export-ModuleMember: Update, ExportList
  • Set-Service: Include, Exclude

• Following variables have been renamed
  • $CommandLineParameters to $PSBoundParameters
  • $PSPackagePath to $PSModulePath

• Packages have been renamed to Modules. Packages folder is now renamed to Modules folder. A module imported into another module is now treated as a nested module instead of a peer module. This allows a new module to wrap or repackage one or more existing modules.

• "Script cmdlets" have been renamed to "advanced functions." The “cmdlet” keyword has been replaced with the “function” keyword. For script cmdlet functionality, use CmdletBinding attribute in the function’s param block. For more information, see about_functions_advanced.

• The Config-WSMan.ps1 script in the $pshome directory has been replaced by the Enable-PSRemoting function. To configure your system for WS-Management remoting, use the following command:

Enable-PSRemoting –force

Note: If you have upgraded from the Windows PowerShell V2 CTP2 release to the Windows PowerShell V2 CTP3 release, to configure your system for WS-Management remoting, type:

Unregister-PSSessionConfiguration * -force;

Register-PSSessionConfiguration Microsoft.PowerShell –force;

Enable-PSRemoting –force

• In the Out-GridView cmdlet, the drop-down list used to filter objects is now called “Query” instead of “Filter”.

• The following changes have been made to Windows PowerShell Integrated Scripting Environment (ISE):

• The name of the application has changed from “Graphical Windows PowerShell” to “Windows PowerShell Integrated Scripting Environment (ISE)”
• The executable name has changed from “gpowershell.exe” to “powershell_ise.exe”
• The profile name has changed from “\Users\<username>\Documents\WindowsPowerShell\Microsoft.GPowerShell_profile.ps1” to “\Users\<username>\Documents\WindowsPowerShell\Microsoft.PowerShellISE_profile.ps1”
• The term “runspace” has been replaced with “PowerShell tab”.

Get it from http://www.microsoft.com/downloads/details.aspx?FamilyID=c913aeab-d7b4-4bb1-a958-ee6d7fe307bc – piping hot!