I love the xpack so far. As a currently top 10 US guild raider I find the raid encounters pretty well done. The world is beautiful as well, with loads to do.
My very casual wife, who also plays is loving it as well. The heroic dungeons are tuned fine for her level of play, and she's had fun doing the achievements and all the quests ect.
Besides PVP this xpack is right up there. It's sure not burning crusade but there won't ever be another like that. I personally think it beat the death out of wrath and cat thus far. With tons more to come.