When I started my RM project, no (though I'd done work on one for another idea or two I had). Now though, absolutely. If there's one thing I've learned at my age, it's that I'm not going to remember everything (although it's a lesson bad habits have kept me from fully realizing). So, if nothing else, the GDD for my game is a record of all my different thoughts and ideas, a place for me to take them out of the roaring, gleeful chaos of my mind and put them into a more coherent space. And good gravy is it long. I have one section that outlines all the planned maps for my game, with only 2-4 sentences describing each map, and that section is something like eleven pages long. Ditto for the basic rundowns of the story-essential NPCs. The script for my game is 120 pages.
I don't feel like GDDs are restricting at all. Remember, they're a living document. They WILL change over the course of development. Even if it's just a place for you to get your thoughts together and outline what you want to do, just that much can help. Now that I have a defined list of the maps my game needs, I can get them produced faster with that sense of direction rather than sit there and be all "How big do I want this town to be? Should that inn have two floors or three?" when it comes time to actually make stuff. And if I want to add on to what I have later, I CAN. Nothing's stopping me from doing more later on if I want.
Although that articy program has me very intrigued. It was even used for something as big as Star Citizen... Definitely looks like something to look into, and would be much better for organizing my thoughts than Word, heh.