Percona is glad to announce the release of Percona XtraBackup 1.6.5 on 10 February, 2012 (Downloads are available here and from the Percona Software Repositories).
This release is purely composed of bug fixes and is the current stable release of Percona XtraBackup.
There are some important bug fixes around incremental backups, parallel backups and backups on databases with the system tablespace being multiple files. The full release notes and details are available here: http://www.percona.com/doc/percona-xtrabackup/release-notes/1.6/1.6.5.html