In case anyone is looking to automate deployment of Nintex solutions (and why wouldn't you?!), you can visit my blog to get a PowerShell cmdlet that imports UDAs into an environment, and retains their GUIDs so that workflows that reference the UDAs also import seamlessly!
Here's the link: The SharePoint Repair Joint: PowerShell cmdlet to Import Nintex User Defined Actions (UDAs)
Cheers,
Marty