For some people, the game changes a lot at level 80. A whole lot of new opportunities open up. New reputations to work on, new instances to check out, new raids to explore and beat, items to chase that you know you won't replace in a day or two. For others, it doesn't really change anything. You pick up your new level 80 spells and abilities and you go right back where you left off, questing in some zone.
Personally, I'm more like that first type. I quest hard until top level, then take a break from it while I work on other things. I quested through Storm Peaks in the Wrath beta, but I haven't done it on live yet. I hit level 80 in Icecrown and haven't done much questing since then, I've mostly been running raids and heroics, finally replacing my level 70 gear. My first goal, though? I wanted the Reins of the Red Drake.