So I thought I'd create this thread for us ;)
The Intro is evocative and thought-provoking. I thought I knew what it would say, but the idea of Khyber's darkest depths leading into the Elemental Chaos surprised me.
But the real meet of the first preview was in Aundair's write-up. This map is simply amazing in that it highlights what part exactly is within Aundair (I've always struggled with this in maps both fan and official in nature. I also struggle with non-D&D maps too ;)). But more importantly it has every location found on my fan map AND THEN SOME!
The Forgotten Realms map was all about removing the clutter. Eberron fortunately went in the opposite direction!
Knowing very little about Aundair,the write-up provided a nice snapshot. I feel I have a much clearer picture of this country, although I certainly won't be writing adventures for it before I get the ECG ;)
Today's preview wasn't very useful for me with Karrnath. Although knowing more about Karrnath then any other country, that's inevitable. I am pleasantly surprised to see Mounts! It could be we'll even get to see elemental airships or even elemental galleons. But even if we don't, today's excerpt would seem to indicate we'll get more mounts, including hopefully some from the Talenta Plains.
Although I do have a gripe about the mounts being in the ECG. This sort of crunch seems ideal for the EPG as there isn't anything about the Magebred Destrier that would suggest its inappropriate for PCs.
Fortunately it should appear in the character builder so my players can access it through that.
The Realms maps look like Elminster took a great big dump on it....
....or they wiped his backside with it. 
:P I eagerly await the ECG. :D