Incremental MYISAM

Unfortunately we are using MYISAM and Innodb at the same time and tables are pretty big. As the documentation says, the incremental snapshot will all ways copy over the MYISAM tables.
http://www.percona.com/doc/percona-xtrabackup/2.1/innobackupex/incremental_backups_innobackupex.html#preparing-an-incremental-backup-with-innobackupex
It looks like when we do apply log, it's copying over the files again and it takes a long time for us.
We are trying to move everything to Innodb but the process is slow since we are storage bounded. At the same time, I'm curious whether XtraBackup will have better support for MYISAM for incremental snapshot(maybe just do the diff)?

Thanks!