I am absolutely thrilled about account wide achievements. Why? Because I'm lazy.
You know this Loremaster thing? Maybe I can do it on multiple toons. Jori - the mage - is 75 quests away from Loremaster of Cataclysm and three zones away from Loremaster of Outland. Naesa - the hunter - is three zones away from Loremaster of Northrend. Jori? She has one achievement for the Northrend quests, because like an idiot I did a couple quests in each zones and complained a lot to Mad that this shit was taking forever, and I was so impatient and obnoxious that he finally leveled my toon to 80 himself because he just couldn't bear to hear me whine one more second. Or just because he's the best boyfriend ever and can never (almost) say no to me. I mean come on, he farmed Darnassus rep for my human mage so I could get a Night Elf mount. And that was back when you had to do quests and turn in an incredible amount of various cloth. No tabards at the time, oh no. But I digress. The point is, I won't have to do all the Northrend quests on my mage. My hunter has done a good chunk of em already. If it works, it's going to save me a lot of time. What's not to like?
It does bug me a little that my mage won't be the only one with ALL THE POINTS. I'm trying to convince myself that it doesn't mean anything. I won't love my mage less. It just means I get shit on my other characters that I'm too lazy to farm more than once. Since we'll be able to know on which characters each achievement was earned, Jori will still be the special snowflake! And whenever I get a "surprise achievement" on an alt I barely play, I won't throw a fit. (Oh yay! But wait, I'm not on my mage! FUUUUUUUUUU!!!!!!!! )
I'm already not even getting my alts all the achievements they could get. I do them once, on my mage, because it's fun. But doing them twice? Not so much. So it wouldn't especially bother me to roll a level one who would have 8k + achievement points. I love leveling, that's why I roll new alts. But it's actually annoying to look at their achievements (or lack thereof) and think : "Crap, I gotta do it all over again!" And then I just don't do it all over again. Because I got other achievements to get on my mage, and I never come around to my less played toons and go "Your turn now. Let's farm ALL THE POINTS."
So I'm excited about account wide achievements. Because I'm lazy. But your mileage may vary.