Don't forget Alfred Bester. The Stars My Destination and The Demolished Man are interesting precursors to Gibson.

He also wrote a fantastic, underrated novel that is definitely his most cyberpunk: The Computer Connection (1975), also published as Extro. It's great fun, and at times paints a future even more callous about human life than Gibson ever described (the main character is arguably a serial murderer, even if he has good intentions). The book was poorly reviewed at the time, and I wouldn't mind admitting that it's "flawed", but it's still one of my favourites.