Has anyone else had a problem with some of the quick items? I can't use the 'q' or center mouse button quick menu... Which means that if I want to use the boomerang blade, I have to press tab, go into the inventory, select the blades, and double click to use them.

Am I just an idiot? Or is this a legitimate issue for someone else?

I didn't have any issues with the quick items. Kind of a stupid question, but are you sure you are equipping and then selecting the right slots? Try changing the bind to something else, anything, and try that. If it works just find a new bind key that is in a convenient location.