Gotta say, in 20+ years of branching and merging using CVS, SVN and then Mercurial, I've never had an issue tracking down nasty bugs. Maybe git bisect on a linear history would hypothetically be a few minutes faster in some cases, but doesn't make it worth all of the extra work and the dangers of overwriting other people's work.

I think the Fossil devs also make a good case that the problem is really a limitation in the tools like git bisect.