Okay, fixed by changing 'gtkd' setting to 'gtkd.lib'.

...Hello World"));
    win.showAll();
    Main.run();
}

After setting Project Properties > Linker > General > Library Files: gtkd

...where the additional hints to dub and  gtkd are very usefull.
(Not mentioning what can...

...problem with graphics and D (other than GtkD, which is a very smooth operation) is...

...OSX, Wx, and Qt. I've got GtkD for all my needs, so I don...

...recommendation is that you try to use GtkD or TkD as they just work.
Also...

...what it took to get it going here:

http://gexperts.com/wp/gtkd-and-localization/

...other cross platform GUIs aside these and (GtkD & DWT), and that is the case in...

Except for GtkD and DWT, D does not seem to be supported by a really...

...blog posts. Posting to D.announce and adding links from gtkd.org would be great.