As getting the ok to migrate source code repositories only comes if the previous service is taken down, I have started to use git svn. Working against several subversion repos and only one git repo made me really like the speed and distributed style of git. Using git svn is easy. Use git as normal, and use rebase and dcommit to replay your changes with the centralized subversion repo.
A colleague told me about a switch you could use when cloning subversion repos. git svn clone -s
The -s is a switch that makes git download and replay the commit history of the subversion repository typically resulting in a much smaller code repo on your local computer as it uses its internal structure instead of downloading all files as subversion does. Sounds nice, but takes forever in bigger projects. So far an import of a on disk complete 4 GB repo with about 2k commits has taken 24 hours.