If you haven't read my post on whether we should have more customizable dialogs in Workflow Studio please check it out (here) and respond to the poll so I know what you think. In that post I mentioned that you could get custom dialogs today in Workflow Studio by leveraging PowerShell. Building Custom dialogs in PowerShell is not easy right now, but there are some projects out there to automate the process using the Visual Studio designer so it is getting easier. I'm not going to cover the specifics of how to create dialogs with PowerShell, but have a look at this Microsoft article for an introduction and then I will show you how to use this concept in Workflow Studio:

http://www.microsoft.com/technet/scriptcenter/resources/pstips/feb08/pstip0208.mspx

As I said, the process of building the dialog in PowerShell is tedious, but fortunately getting it into Workflow Studio is not so hard. Workflow Studio has a task called "PowerShell script" that can execute PowerShell script directly:

 
Just drag this task onto your workflow and paste the code from the above article into the "PowerShell Script" property. Now when you run your workflow you will get the dialog to appear. Pretty cool...
 
If you left all the defaults on your PowerShell Command task then you will also have the results of $x (the input string) in your $Output variable and you can use that in subsequent tasks.
 
In future articles I will look at how you can use this concept to create more complex dialogs and pass more complex objects out, but try it out and let me know what you think.