Where BZR makes parallel development in separate, but periodically synchronized repositories much easier than CVS, it falls on its face with having robust, complete, bug-free code. BZR is missing useful minor features available in CVS for reporting status and history, for example. BZR sometimes crashes due to bugs in code. (The last time CVS crashed was before you learned to read and write. :-)

er, really? crashed? hm. i've used bzr heavily for multiple projects for several months now, and it's NEVER crashed on me. the only bugs have been fairly minor, and were resolved pretty quickly, and really didn't slow down my usage of the software