I really enjoyed the one week I got to play it. Yes, item lag was an issue at times but hey it's beta. My first 20 levels I thought the quests were kind of repetitive (incursion type quests like kill x amount of y mobs or deliver this not to person p at location z).
Then I did my first instanced quest, VanCleef in the deadmines and I was blown away. Awesome stuff. Not to mention the Paladin quest available at level 20 which is a fairly huge undertaking. Sadly I didn't get to finish it before beta closed.
Keep in mind that most storydriven quests are NOT in beta and are tested internally since Blizz didn't want to spoil too much. So there should be plenty more to come in retail.
I will definitely buy and play WoW but not until it comes out in Europe. Mainly because it's a hassle getting my American friends to pay for my account and secondly...let them deal with the crap (read bugs) on launch day and the following weeks
--jaded