The biggest problem with git is the scalability. We currently use it in an awsautoscaled environment. When the servers come up, obviously nothing is on /mnt. This causes git pack to cause high com and high io in the master as it computes from commit 0. This can be solved using shallow copy, however, there are major bugs with that if you use branches and you risk deploying the wrong code to the wrong server.
So what is the solution? We are still working on a good one. Right now wend up mounting an nfs mount when the server bootstraps and copy over a base image of the repository avoiding git pack-objects and the delta overhead which goes with it. Is it the answer? No. The hunt for that continues.