I vastly dislike timeline resets. It's a personal, and I think perfectly valid, annoyance. Of course I buy work for the quality and not the canonity of it, but everything is being rubbed out, not just bits here and there. I like taking time out to read through a full, long running series to know where characters are and how they got there - I once went through 400 issues of Uncanny X-Men, and have almost 1,000 Spider-Man comics released since 1994 sitting in my loft that I like to go through when they're referenced in current continuity. A large part of the enjoyment for me is getting lost in a character or group's mythology.
It's something I've done for a long time. Maybe it's a history thing, maybe I'm an oddity. I don't really care much, but it really annoys me to see people disregard what's gone before them, and I like a sense of continuity in what I read. It still grinds my gears that they did a hard reset on so many aspects of Spider-Man with the One More Day/Brand New Day pish that they pulled a few years back, and the outcry from my fellow geeks over that fiasco shows I'm not alone at least.
I mean, I wasn't nerdy enough to boycott Spider-Man like some did and I'm always down for new ideas and storylines (I loved Superior), but to simply wipe away such a large aspect of the character for two decades is ridiculous, and removes a vast amount of the character's development in my view.
What happens with a timeline reset, in my experience, is that the company doing the reset take the opportunity to churn out lazy re-hashes of events and storylines that have already taken place with the odd change here and there, and that vastly diminishes my enjoyment of the output of that company. Ultimate Spider-Man was a nice change in pace from modern AMS but if it had taken the place of the main comic I can't say I would be as warm towards it.
It doesn't help either that I'm becoming quite disillusioned with Marvel's current practice of shoving two or three events per year, or even at the same time, down the throats of the audience, forcing us to buy multiple one shots if we want to keep track of what's happening. A timeline reset would just be the straw that breaks my ability to care.
Of course this is all hypothetical, the Incursion event might not lead to anything like what we're speculating on.