I'm not a visual guy, so I really need the 3D Visualizer to help me out a lot. Since I use multiple lights and types, including moving heads, for me, it's essential to see I've got the right concept down.
But really, to each their own. For me it's a very helpful tool. Despite all the assumed bugs, shortcomings, flaws or errors in it, for me, it provides an accurate enough picture to see that I'm not totally hosed in my design.
In my case, for some reason my mind reversed stage right/left, so most of my scenes are backwards. I've got to undo this and redo it right. Most are simply tweaks, but there is one scene that was a pain, but alas, it will be done and it will be done properly.