A very interesting review of the history. I do wonder why it didn't take off to a greater extent than it ultimately did. Is hiring full-time people ultimately detrimental to fostering a development community by giving the impression of being an internal project, or was this mainly reducing existing developer time as they got involved with other projects within Canonical? The other factors appear to be the copyright assignment (but this came in relatively recently in its history). Or was it really just a case of being unlucky, and not being in the right place at the right time?
I should have been a bzr user, given its origins with tla/Arch. Back when tla was in its infancy, I converted all my code to Arch repos, and started all my new work with tla, and used it fairly exclusively for several years. tla had many faults, but it was unique at that point, and was the only realistic alternative to CVS (before SVN was ready). baz/bzr would have been a natural upgrade path, but /at the time/ it always looked like the repo format changed so often that it wasn't ready/safe for serious use (at least, that was the impression I received). All these repos were eventually imported to git, some with a intermediate reversion back to CVS/SVN. But I do wonder if it wasn't for the initial perceptions of the project, they would have otherwise have been in baz/bzr for the last 6-8 years, and if this applied to other projects as well.
With hindsight, I think ending up using git was the best choice technically, even if the "UI" is not as friendly, but things could have ended up quite differently 6-8 years ago if bzr had been the obvious choice.