Tracking path by their content is not always good... It couples content changes with intent changes. If I need to make a copy of directory and then make the copies slowly diverge until they have nothing in common, I may want to mark which is for original intent and which is spin-off.

Branch history is not an inherently local thing.

When I have feature branches for recurring tasks, I will probably call them always the same. I will sometimes merge them with trunk and sometimes spawn them from the new trunk state. Later, I may wish to check whether some change was done in trunk or in the feature branch - it is quite likely to provide some information about commit intent. I can get it in every DVCS I know except Git easily - in Git I need to track DAG to get this information.

About succesful-build branch: for some projects I try to update to trunk head, and if it gives me too much trouble I look for closest previous revision which I can expect to work. In Monotone I simply mark some development commits as tested enough, there is a simple command to get all the branch.tested commits from the last month. This information says something about a commit, and to lose it I have to do something with the certificate that states it. In Git, rev-list behaviour depends on many things that happen later.

Linux kernel history is too big for any of the things I say to make sense for it. But in a medium project, I want to have access to strange parts of history to find out what happenned and how and what did we mean.