NOTE: I recently wrote a review of using several major IDEs with IronPython: http://www.voidspace.org.uk/ironpython/tools-and-ides.shtml
(Including SharpDevelop, Eclipse and PyDev, Wing, Visual Studio and IronPython Studio)
I'm not a big fan of IronPython Studio it's not really production quality in my opinion. The designers target IronPython 1 and the generated code require changes to run them on their own with IronPython. Having to modify generated code is never good!
I use the designers with Visual Studio to generate C# and then subclass in IronPython to actually implement the functionality.
For working with IronPython any of the 'normal' Python IDEs will be fine. I like Wing because the autocomplete is the best I've seen in a Python editor. You can also teach it to do autocomplete for .NET libraries (by generating PI files).
For working with Wing (Wing personal is free - but the professional version is better) don't set your interpreter in the project settings to be ipy.exe though because you lose the interactive shell inside Wing which is very useful for trying things out.
This means that you need external tools to run your tests, launch your application, but using the Wing scripting API or the OS tools to integrate these tools into Wing is easy.
Komodo, SPE, Vim, Emacs are all editors / IDEs with Python integration and will all work very well - which you prefer depends on your tastes and workflow.
Do you have any other requirements for an IDE?
For general IronPython development I use MSBuild to provide build automation, Wix for building installers, Pyc (IronPython compiler sample) to compile to binary assemblies, and a custom executable for the project that is very thin wrapper around the IronPython hosting API written in C#. An editor / IDE is only one of the tools used - and a general Python IDE should serve you well.
[1]: NOTE: I recently wrote a review of using several major IDEs with IronPython http://www.voidspace.org.uk/ironpython/tools-and-ides.shtml