I didn't really get on with Age of Empires III - pettily, I was turned off by its fonts - so wasn't paying huge attention to the second add-on pack. Then three things happened which changed my mind.
Firstly, they released a demo of it. I'm always interested in free stuff. Secondly, Tom Chick got excited about it. When it comes to anything to do with the RTS, I'll trust Chick a long way - especially because he wasn't exactly enamored with the first. Thirdly - and this really shows how off my radar it was - it's actually being primarily developed by Big Huge Games rather than Ensemble. Who, according to Tom, have been doing some really neat things. Including hotkeys, but Tom always gets excited by hotkeys. If a key's not hot, he's not into it.