The chunks of level that the quests eat upa re quite insane. I now have a level 16 warrior and level 14 druid (who is almost 15). If i turn in like 3-4 quests it gives me an entire level basically. I hit level 14 in under 6 hours played with my Druid. Im hoping to get them alot of levels this weekend.
The one thing that is alot different is that I am not really used to the Horde areas. I am not really sure where to go after the Barrens, so I guess I will have to look it up online.