I've done every quest in Hyjal, Vashj'ir and Deepholm now.
It is a little annoying, in how linear the game is.

Each area has a set progression.
And the next area does not open until you complete the current area.

If you are stuck on a given quest, or just plain do not like it and are not going to do it.
Pretty much the rest of the zone is done.
One bugged quest or quest which you cannot do/don't want to bother with, and the zone is done.

Some of the quests are very fun to do... but it sucks how you are railroaded down a single path.

The lore is ok; I read every quest the first time through a zone.
The cutscenes are ok; but wish there was a bit more warning for those, as I quest with mp3's going and warcraft sound off.