This strikes me as a very hard thing to write about a project with which one is intimately involved, and which Jelmer manages admirably well. I only hope that if I'm ever in such a position I can create that much value on the way out.
There are bzr features mentioned in this that I didn't know about, as someone who only uses bzr very casually. One is handling of the the left/right sides of history, where one is simple (and presumably, good for rebasing) and the other contains all the detail of intermediate commits. It's apparently well ahead of git in this area.
I think it's important to keep in mind that, as the VCS area contracts and consolidates (which it clearly has been, for years), there's danger of losing innovative stuff like that. Another example is that I think bzr or other VCS developers would claim to have merge algorithms that are often better than git's for text files. It would probably be fruitful to find these ideas and bring them into git as add-ons.