I was on 611 on 2/22 and we were delayed 9 hours! We left the gate on time but as we taxied out to the runway we left the main taxiway and the captain came on and said we may have a problem with the main hydraulics system. We eventually returned to the gate and got off the plane. This is when the fun started! We were given 6 different ETD's! 10AM, 11AM, 12PM, 2PM, 3:30PM, 5:30PM! At one point, there were no DL representatives at the gate for well over 2 hours! We finally boarded at 5PM and took off at 5:45PM! Before the door was closed, we we're told we were being given a $50 travel credit! Talk about adding insult to injury! We finally landed in HNL at 9PM! Thanks to DL, we lost a day of vacation!!!!