Patrick,
We'll have more information and examples when we ship EG 4.2 early next year. We have a number of improvements for those seeking to create custom tasks, including a toolkit that makes the job easier, and enhanced APIs to provide more access to information in your EG project.
Plus, since EG 4.2 uses the .NET 2.0 runtime, you will be able to build custom tasks that target .NET 2.0, 3.0, and 3.5 - including using features such as WPF and LINQ, if you want.
Chris