Parth announced bzr-grep 0.2.0.  Amongst other things there are performance enhancements such that Eli says:

Thanks, this looks great. I just tried it on Windows XP searching for a fixed string in the Emacs repository — took 28 seconds with a cold cache and only 7.5 with a warm cache, which is impressive.

By contrast, “grep -F -R” (with suitable –exclude patterns, to prevent it from searching binary files and inside .bzr) took about 12.5 seconds with a warm cache.