I think you're right about Ditko's seminal work on Spidey, and I also agree he got a bit sloppy toward the end. That was the point when he and Stan were feuding over the identity of the Green Goblin, leading to Ditko's quitting the title (and the company). Ditko is one of my favorite artists, but when he is disinterested in a strip, it really shows in his work. Maybe we're all that way, eh? I remember reading some of 70s and 80s superhero work (like his mostly wretched Hulk or ROM Spaceknight -- the latter saved only by some pretty P. Craig Russell inking) and wondering if it was the same guy who had done the lovely woodcut-like Warren work or the more traditional (but still great) Shade the Changing Man and Tomb of Dracula magazine #2.