It was Cataclysm launch day. This was the first launch day which the launch time was 3am for those of us in the eastern time zone. I of course planned to stay up and get ahead of the leveling curve. I was leveling up with Safiree and we started in Hyjal. This was her first "real" expansion leveling experience, and I say that because the way I level on day 1 is probably not the norm, Sure I love to enjoy the zone and want to know the quests and the questlines, but I am still in go go go mode.
We are going through the zone fine getting ahead of everyone when I believe it was around 7am and Safiree asked me if when were going to sleep. I said "no" we have to keep leveling when she assumed I was joking. This went on for about an hour and she was asking me what seemed every 5 minutes and she got to the point where she couldn't actually continue and her was walking into trees and flying into cliffs. Yes this was actually happening. It was quite amusing to me not so much to her. I told her she could sleep for a couple hours and then we would get back to it.
She did end up sleeping for about 4 hours until the "leveling nazi" made her come to and level some more. I know she appreciated my craziness in the long run and it caused the day itself to be full of some amazingly hilarious moments which I will always remember. Silly deaths due to exhaustion or being in a frame of mind where you were actually unable to read the quests. Even the moment when my Shadowmourne was replaced.
This was the only time I level day 1 in a party and sure it might have been slightly lower because sometimes slackers have to sleep, but it was pretty awesome as well. So I would say no matter how you choose to level enjoy it in your own way and make sure it is something you can remember and tell stories about later on.