With all the improvements to the leveling process, you'd be hard pressed to find a player immune to the ill effects of altoholism. Everybody (and with the new free-until-level 20 system, probably their grandmothers too) is rolling that one class they've really, really wanted to try but were too put off by the leveling process to actually do so. In many cases, they are rolling several new alts. All those alts adds up to a lot of leveling -- far more leveling than the current content can support, even. Even after three alts, many find themselves having exhausted the zones currently available in the game. It can get stale very, very quickly.
To prevent the dread condition known as burnout, alt-heavy players have to mix things up as they level -- different zones, different continents, dungeons, Battlegrounds ... Anything to break up the monotony. Personally, while there are several zones I never skip -- Zangarmarsh, Netherstorm, Howling Fjord and Grizzly Hills, for instance -- I make an effort to play through the zones in a new order, hopping continents as often as possible, and never running dungeons or Battlegrounds. Sure, the story may be massively fragmented this way, but I've played through it before. I know the story; I'm there for the gaming aspects the second time through. Sure, dungeons and Battlegrounds may be fun and provide quick experience, but questing lets me go at my own speed.
When you level alts, how do you navigate the zones? Do you have a select few favorites that you always level through, or do you try to forge new adventures in new zones as you make your way to 85? Or do you bypass the zones entirely and opt for dungeon or Battleground farming?