One of the biggest problems I have is that, from time to time, I suffer from extremely painful bouts of insomnia. I've had this issue ever since I was a very young boy, and it still reoccurs from time to time. This has lead me to discover the joys and pains of logging on to play World of Warcraft in the middle of the night. Since I tend to play on servers in the same basic time zone as I am (Edmonton, Alberta if you're curious) this often leads me to discover that it can be an entirely different world when most of the server is asleep.
One of the large positives is that I often catch the Auction House when a bid is about to expire - I got my BE pally a Sword of the Magistrate for practically nothing not an hour ago, for example. It's also a lot easier for me to do quests that involving farming mobs that are otherwise popular either because the quest itself is popular or because they drop something folks want, like the elementals in the badlands that everyone and their parents tend to farm.
There are some big downsides, though. For starters, instances? Forget about it. If I can find two people on at my level at any given time it's a small miracle. Also, when you're bleary eyed from lack of sleep, that may not be the best time to try and do an annoying escort quest. Admittedly, I tend to find escort quests in general to be the second most annoying quests in the game, with "bring me x number of the eyes/hearts/brains of y" being the absolute worst, but I want to level my characters so I do them anyway.
Is anyone else out there playing on the graveyard shift? It sometimes seems like I'm totally alone, but a few folks must be toiling away alongside me. Do you prefer it or are you just there sometimes? What's good, what's bad about it for you? I sometimes like the relative peace and quiet, but I miss being able to get a Sunken Temple group when I need one. And I can't say that playing the game makes me feel any more rested.