This GUI concept is very nice. Far more appealing to me than the 'Flat' GUI.
I love the combination of wood, iron and stone. The colors aren't harsh. The chiseled stone effect when an action is highlighted is a very nice subtle touch.
I myself am not keen on a PIE menu as the others suggested. I think it feels too.. 'Xboxy'.. for lack of a better word lol.
One person suggested releasing an editable template of the GUI for modders. I think this would be a great idea, it could add some great personal touches and really help with immersion in your character and chosen profession.
An Alchemist's GUI being very different from say, a Logger, construction builder, a blacksmith etc.