Just tried the auto upgrade to 1.2.1 and it crashed my site. Got the site back up and tried to activate the plugin again and received the following:
Warning: require_once(/*my site info*/wp-content/plugins/sabre/classes/sabre_class.php) [function.require-once]: failed to open stream: No such file or directory in /*my site info*/wp-content/plugins/sabre/sabre.php on line 42
I was previously running 1.2.0 without any issues. Deleted the plugin directory via ftp and re-uploaded 1.2.0, activated, and I'm back up and running.