Finally we can fire up an IDE to develop managed code with those nifty XML based InfoPath forms. MS has posted a toolkit in their download area so that you can use C# or VB.NET to develop InfoPath based solutions. Very handy.

Here's the official overview:

The InfoPath™ 2003 Toolkit for Visual Studio® .NET is designed for developers who are interested in creating form templates in InfoPath 2003 using Visual Studio .NET 2003.