From P4 to Git

Hello,
I am investigating the use of Git in a setting where we:
 1. branches a lot
 2. have a very large codebase

Given Git is developed to handle these 2 issues, I suspect it would be a very good choice, but I need to gather some experiments feedback and hard figures on how Git performs (storage use, necessary bandwidth/resources, maintainance of repositories, cleanup & gc...).

For the experiment part, I am started working on it but would be interested in other people's experiences.

For the figures part, I think I read somewhere there exists some statistics on Git usage for Linux kernel. Is this correct ? If true, where could I find them ?

Thanks in advance for answering my (maybe pointless) questions and for producing such a nice piece of software.