I just completed an upgrade from 1.0.0 to 1.0.5 but there were a few issues, these might occur for others so I've listed them here:
1. Bind won't start due to duplicate entires for BASE_SERVER_VHOST, to fix I had to edit /etc/ispcp/bin/working/name.conf and remove the duplicate entires for that host, and copy the file to /etc/bind, followed by a restart of bind
2. Emails from control panel don't get delivered due to mail not getting generated correctly. The From: header gets set to DEFAULT_ADMIN_ADDRESS correctly but in the php.ini it's set to webmaster@BASE_SERVER_VHOST on the sendmail line. This means the mails come from webmaster@BASE_SERVER_VHOST.
If like me BASE_SERVER_VHOST doesn't actually exist as a domain it won't get delivered (depending on email setup), so you have to set the sendmail line in php.ini to DEFAULT_ADMIN_ADDRESS.
A better solution for this would be to not use mail() and use a library like phpmailer to mail the mails as these would get generated correctly, or by default the php.ini would use DEFAULT_ADMIN_ADDRESS for the master setup.
Other than that the upgrade went smoothly