You are just a few simple commands away to start using all the local power of git (local commit and rewind, stash…) over an existing SVN repository.
I say local power, because obviously, SVN being not as powerful as git, you’re still limited in what you can do without breaking everything when you try to commit.
A simple and effective guide can be found here : http://svnrating.com/svn-to-git-migration/
Note that on large SVN repository, the first checkout/clone can take hours, or even days. On our 2400-commits-large, several-Gb repository, the first clone has taken a few days, but it was making my (bi-Xeon + 16Gb RAM…) computer hang a few seconds or minutes every 15 minutes or so. Maybe you’ll have better luck.
But once it’s done… it’s really awesome.