This was the backup for version 2.1, but I made a couple of minor changes and it now works on MS2 instead.
I made backups using pure sql, ZIP, and GZIP and did a restore using all of them. I tested by deleting my users and they were then restored from the backups. This also allows the download to be done using the zip options or pure sql.
Just drop the backup.php in the admin directory (rename the original and back up first). Use at your own risk.