Once I finally reached 80, I felt so accomplished and at the same time so behind. I still had not finished all the Northrend quests and needed to get going on heroic dungeons, maxing my tradeskills and maybe working on some achievements. Now that Cataclysm is coming soon, of course, we all have our bucket lists to be concerned about, as well.
Sometimes this becomes frustrating. I love to make myself to-do lists, much like collecting quests in my log -- but even more so, I love crossing things off the list that I have accomplished. With WoW, I always seem to feel like I am just trying to keep up. With more and more things about the game that I discover I want to accomplish, my to-do list grows longer. However, I guess that is inevitable when you play a game "that never ends."