WPF or WinForms for occasional programmers?

I'd like to move my project's ActiveX controls to (preferably) WPF or WinForms. My customers aren't expert .NET programmers, but they're able to use WinForms to do basic drag-drop to use my controls. I've experimented with the VS 2010 WPF designer, and it seems like the drag-drop experience is much less intuitive than WinForms.

Is it realistic to expect occasional programmers to be able to use the WPF desi开发者_开发技巧gners in Visual Studio (or Expression Blend) to build these kinds of simple GUI's? Also, what's the simplest available WPF designer?

It depends on how familiar you are with WPF or WinForms.

WPF has many advantages (full transparency support, etc.), but surely is more complex than WinForms.
In addition, WPF comes with a totally new programming experience: Without using patterns like MVVM you soon will be lost as things don't work as in WinForms.

To your customers:
If they are able to target at least .NET 3.0 you can provider wrapper controls using System.Windows.Forms.Integration.ElementHost.
Thus, they could profit from using everything "as before" and you could profit from a more powerful UI-API.

Expression Blend is a much better WPF designer then Visual Studio 2008. Visual Studio 2010 is slightly better than 2008, but Expression Blend has either Visual Studio version beat.