I took that cruise from Bari to Patras this summer. It was a blast as long as you have a blanket, and booze. It helps i dont remember waking up, but make sure you are awake for your stop. If you are going to corfu, the stop will roll around about 6 am, and the stop for patras at about 9am.
The drinks on the ship are expensive so stock up with a jug of wine or a case of beer. We had 15 people from Georgia to Romania drinking with us by 10pm