I knew all along that I perform better in the afternoon than the morning, so I selected a 2:00PM start time. I know this time probably doesn't suit a lot of people, because many people lag in the afternoons. But I generally have a slower start in the mornings, so I went with an afternoon time.
Actually, my preferred time would be late evening. That's when I've always done my studying, during college and law school. Unfortunately, they didn't offer a 10PM start time.
I did great on the SAT & LSAT with their standard morning start times. Here's hoping that I do well on the GMAT with an afternoon start time. Less than a week to go for me.
I'll let you know after I take it whether it was a good idea. How long before your exam Haas?