Although I was always a Marvel guy, I knew who Denny O'Neil was when he took over The Amazing Spider-Man in the early 80s. I don't know how I knew of him, since I had never read his DC work and, back then, such information wasn't easily accessible, but I knew he was a big deal.
I like his Amazing Spider-Man work, but I do see why it has a poor reputation. I loved his Daredevil run. Micah Synn was a really interesting villain.
I read some of his legendary DC work well after the fact. It's great stuff out of context but even more memorable when you look at the historical significance. Definitely a giant of the industry.