To your second point, I remember when git was announced. I remember it was such a breath of conceptual fresh air over what I had been using (svn, mercurial) for me. I use it because it makes a lot more sense to me and how I work, and I've never worked on the linux kernel.
never used it, but afaik mercurial is basically git's doppelgannger - functionally they are identical. Am I wrong here?
No, doppelganger seems like a pretty incorrect term to choose here.