Loving SO. One of the best moderated site in the world. Yes it's not perfect but i've yet to see a site as big as SO with a better moderation,given all the crap that get posted and fortunatly moderated.
One thing i wish I could do is to star a question in the question listing without visiting the actual question,so i can pick it up later,like a quick bookmark.Also i'd like to see more questions per page.
I have noticed some of the issues mentioned by others, like the overly zealous duplicate hunters and brainless comebacks like "You shouldn't do it that way". That's just line noise to me. I fast forward past it and find answers that save me hours of time.
It seems that someone out there has already asked nearly every question I come up with. There's not always an answer that I can use, but at least it's good to see someone else formulating my question a little differently.
I guess I don't really fit into the OP's 1-4 categories. I'm just a person who finds SO useful about once a week or so. I don't have the time or the deep knowledge to be answering questions on a daily basis and racking up huge karma. Just thankful the service exists, and have put in my 2 cents a few times when I had something useful to contribute.
One thing i wish I could do is to star a question in the question listing without visiting the actual question,so i can pick it up later,like a quick bookmark.Also i'd like to see more questions per page.