Is Rsyncing git repo good enough backup solution?

rsync is a good solution for this. It may be a good idea to run git gc and git repack (neither with any arguments) before doing your backup; this may significantly reduce the number of files, and increase the chance of the data not changing too much by next time. Neither will lose any data.

See http://sethrobertson.github.com/GitBestPractices/#backups for a write-up of why doing this with git isn't such a good solution.

rsync is interesting if you really want to backup everything (including hooks and private files).
However:

• it doesn't guarantee the integrity of your repo once sync'ed (ie is git still working from the rsync'ed repo?)
• it has a higher probability of data corruption (you have to save many many files)

A nicer (and cleaner) solution would be to use git bundle (which is essentially a bar repo seen as one file).
You update your local bundle, and save rsync it to your remote media.
Except that, this time, you only "rsync" (actually a simple copy is enough) one file.
And you can directly clone or pull from that one file, that bundle.