Thought I'd weigh in:
What's your relationship to Type 1 like?
No particular relationship. The low points annoy the hell out of me, but healthy One is my highest ideal. (Most of this is based on theory rather than experience).
Do you know any Ones?
I think my grandmother was a soc-1w2, very healthy and a lot of fun to hang around with. I took shelter with another 1 for a couple months once when I left my parents' house. She was mostly cool and really sociable, but harbored a lot of resentment about things I honestly thought were quite piddly--not sweeping the crumbs into the garbage for instance (the sort of thing in life I'm hardly aware of). I still like them both, though.
Did you once think you were a One?
I never did. I considered it for about 5 minutes since I can be quite perfectionistic, am prone to frustration, and apparently hold rigorous standards that other people are far more aware of than I am...but I simply lack those motivations and don't identify much with core 1 issues.
I did type as being 1-fixed when I was typed at 6 in order to account for that connection. But it's simply not the way I tend to handle my anger and it's not my overall outlook on life.
How does it feel to integrate to One?
More productive--you're actually taking action to complete your ideal rather than just wallow in thought and fantasy. At 1, I pride myself on being able to be super objective, fair, and rational when dealing with crises or other life situations.
In my case, integration can also involve "self improvement"--which is actually much harder for me, because that generally entails me "fixing" something inherent in me that I feel should not be violated (becoming more "sociable" when I'm clearly cut out for being a loner skulking in a cloud of gloom on the margins of society, for instance). This can feel like "selling out"--every time I've had to do this, it's been intensely sad, painful, and repulsive, but ultimately has led to enormous personal growth and a broader perspective on myself and life. I always wind up being glad I changed something.
The low side of 1, though, is just criticality and judgement, using moralistic arguments about what people "should" do to cover up the fact that I'm feeling envious and deprived of everything they have. Cut someone down to size. We're equals now. (I feel like the DoD/DoI theory goes both ways).