After consideration, I've moved hello to bzr. In the end I was swayed by its greater accessibility to beginners (as hello should be beginner-friendly), flexibility of usage (centralized or decentralized) and licensing. Weighing against that was the more widespread use of git, and in some nifty git-only functionality in gnulib. I noted that bzr plays nicely with git in all the usual ways: it can import/export and use a git repo directly as a foreign plugin, thus allowing users to move from one to the other in their own way and at their own pace.
-- http://rrt.sc3d.org
