I have leveled 2 Horde toons to 80, my Warlock and Paladin. I generally don't read quest descriptions, yeah OK kill boars I really don't care why. Playing through Northrend was different, the quests fit together a lot better, and I found myself getting into the story. The high point for me was initiating the Taunka into the Horde.
So when I made a DK I decided to give the Alliance a try so far I am kind of bummed. I have been able to get into the non heroic dungeons, and that has been nice, but lorewise I hate Alliance.
Blizz has really seemed to go out of their way to make Alliance xenophobic and stupid. I haven't really enjoyed a quest line or particular storyline very much. It could be that this is because its my 3rd time thru Northrend, I don't know.
(PS I am not leaving a zone until I get the quest achievement. I have BT, HF, and DB cleared. I think i mit hit 80 before I touch Sholazar, Icecrown or Storm Peaks.That has been pretty fun.)