How much forward progress -- meaning, substantive changes in story structure or characters, changes with weight that last -- has there been in ASM, measured over the entirety of the publication? As opposed to a revolving-door approach -- there goes Betty Brant for a while; oh, here comes Betty Brant!
Part of the recent complaints have been about the retrogressive nature of the Spider-Man revamp. The "Supermanification" thread deals with this. I don't think that the renewed aspects that people like -- the brighter look, more humor, elimination of mysticism (heh) -- don't seem to apply to this question, since those are variable story ingredients that any writer could throw into any stew, without any of it representing actual change.
Is forward progress even possible in an MU? I know others have spoken about the illusion of change, but after a while adult readers get tired of that. The stories just become futility in cycles. I would give the relationship between Chuck Bartowksi and Sarah Walker on Chuck as an example of this. After a while, viewers want resolution. Some of the posters seem OK with only the illusion of change, as if certain readers would get satiated and move on, while new readers hopped on the train. But Marvel can't want that. Surely they want to keep as many readers as posisble.
ISTM that part of Spider-Man's appeal was the ingredient of actual change, not just the illusion of change. He isn't Superman, in that way. But I don't know if it's a curable "problem", in serialized fiction.