I'm looking for articles (or other reading material) on the topic of fat client applications with a web UI layer. Open-source projects that use this architecture would be very interesting too.

Such an application would embed one (or more) browser-window(s) (chromiumembedded for example). You would need bidirectional communication between your web-UI and your domain model/services. I think this allows quick prototyping the UI, a clean separation between logic and UI and potentially easier portability across platforms (compared to WinForms for example).

But that is just my view, I was looking for the view of people who have been on that road.

An example of an application using a web-ui layer is Light Table. Unfortunately it is not open source (at this point?).