Haven't seen anything about it here but it seems to solve one of the problems with GWT - the fact that you have to write Java code to generate your GUI. Instead this software allows you to design the GUI using drag-and-drop tools - a WYSIWYG interface.
I'm not trying to sell the product, by the way.
I just want to know whether it works as advertised, is effective, easy to use, etc?
Anyone have any experience to answer these questions?
I don't think that the lack of a GUI editor is a problem with GWT. Consider HTML, there are plenty of WYSIWYG editors for that (like Dreamweaver) but most experienced web designers don't touch that stuff with a barge pole, they hand code it. Not because they're masochists, but because they want control over the source, they want to make it clean and readable. Coding is a scientific artwork, best left to Human Beings ;)
I tried GWT Designer very early on, and I found that it was fairly poor (and only worked on Windows because it had some dlls that went along with it), but things may have changed drastically since then.