Icecrown is the coolest zone in all of WoW, but it's a special zone which requires some complicated stuff to be going on serverside, which leads to characters losing follow at certain points. If you do the quest chain for Icecrown, you'll see that the zone really changes based on your progress, with an entire new town and flight point being set up after about 20 quests. Unfortunately, you need to do a couple of bad collections along the way, but after that it's a motherload of super-easy exp and great quests.