For the Arora project one of my default git hooks it to build the project, tools, manualtests, matching autotests (and run them for regressions) before each commit. This slowly increased to the point where it was taking minute or so (over the course of just a few weeks). Taking a few hours I cleaned it up and had it back down to just a few seconds at most and on average less then a second. I did it the more correct way and did some quick profiling to see where the time was spent and then fixing that (mostly that object files that could be were not being re-used across different project when building). Making sure that I never break the build on any commit really pays off. There have been less then a dozen build breakages in the entire Arora commit history due to this git hook and those I believe were either build breakages introduced on OS X where a.cpp == A.cpp (breaking it on win/linux) or when we broke the build against older versions of Qt so it build against 4.5, but not 4.4. When you have a quick build time doing things like build hooks are very possible and useful.