We use several 1/2 square drive impacts, so this makes sense for those times I need more screw guns. It makes the square drive more versatile. If I'm working on a project where I need different tips, i can have multiple tools, each with it's own tip. I put one in each square drive kit so if I'm on the job and need to put in a screw I can without running to the truck for a screw gun.
The down side is it makes the tool longer, there is some wobble, and my square drive impacts turn slower than the 1/4 inch hex drive tools. That said, this little attachment is very well made and i am very happy with it.