This is a great knife and my favorite. PutnamEco is right I wouldn't want to use this if I was a drywaller to many parts and drywallers don't need retractable blade. I am a carpenter and use the knife for general duty work. Cutting the paint line where the trim meats the wall, opening containers, occasional roofing, occasional drywall, sharpening pencils. The knife is small and light enough to fit in a pouch the blade is easy to change without tools and it carries 5 or so extra blades, so no running to the truck for a sharp blade.

I used this knife about three years ago, until they came out with a newer version. (10-788)
I quit using this particular style of knife, due to how hard it was to clean out drywall crud.
mainly all the small parts that had to be held in alignment to be correctly reassembled. The Knife did function correctly until the retract mechanism jambs up.
I've always disliked how much the blade moved side to side, it sometimes follow the grain when I used it for marking cut lines.