Specifically, porting changes between multiple branches in svn was a nightmare. E.g. if you have three different branches (two releases and a develop), and you need to make the same bugfix on all of them - extremely unpleasant. I ended up writing my own diff/patch management system to keep track of bug fix patches, so that I could reapply them at will on other branches.

Git instantly made sense to me. It incorporated how I already thought about repositories and diffs. The DAG structure made sense. Merging made sense; rebasing made sense; everything made sense, almost instantly.