Braden, it's 1/2". I started working around the main garage with sheathing grade, but that stuff was so crappy the edges weren't even straight. I found BC Sanded for $2 more per sheet when I did the workroom. It's thick enough to give enough hold to screws and dowels for all but he heaviest items.
Eric, thanks, coming from the quinticential anal retentive shop designer it is a compliment.
Bill, don't fret too much, I can make a mess with the best of 'em. Though I have grown to appreciate some organization as my workbench at the old house generally just got filled with crap till I was working sitting on the floor.
If you all didn't gather, the general organization is heavily used tools in reach and the upper areas out of reach are filled with the tool archives...