It is not necessary to use IronPython Studio to debug IronPython code in Visual Studio, however if you want features you're used to in a Python IDE (autocomplete, go to definition, call tips, integrated interactive interpreter and so on) then you probably want to look elsewhere. I use the capable Wing IDE, but a custom solution for IronPython would be an interesting project.
This is where Davy Mitchell steps in with a new project called Davy's IronPython editor.
The screenshot below shows the editor pane (implemented with the Windows Forms SyntaxBox component) and the class browser.
You can download Davy's IronPython Editor from its Google code project page:
The project intentions is to create a editor along the lines of SPE or DrPython for the IronPython world. DIE is easy to deploy (zero install) and will run from a USB key etc.
This project is targeted at IronPython 2.0 and is developed on the Windows Platform. Currently it uses the SyntaxBox component (LGPL) for the text editing component.