It's the first time I've logged in more for more than a few minutes since Cataclysm went live, and my first reaction was OMG they CHANGED EVERYTHING argh argh change bad eek!
But actually I think a lot of the changes are fairly isolated, and it's just that they redrew all the maps using different iconography. Which is still somewhat disorienting to me, but not as bad as I had thought. I may still set my hearthstone to Thunder Bluff for a while, since Orgrimmar is SO different and I have no idea where anything is.
There are also SO MANY new flight paths to pick up, and I'm going to feel compelled to get them all even though they are mostly useless since all my quests are in Outlands, I can tell already. Bother. I picked up a few in northwest Kalimdor.
And then I rescued baby murlocs. La!