[Tested in both mid 2011 Imac and early 2011 MacBook Pro]
My friends, I've been running this game for over a month (The Forgotten expansion, too) on Mavericks and the experience is bliss. However, the following must be done in order for this to work:
As probably many of you have experienced, when you install Steam and AoE through the CrossTie everything seems normal; but when the time comes when you need to press the play button nothing happens. There's an easy fix to this, you just have to - click properties - browse local game files - rename Launcher.exe to 1Launcher.exe - rename AoK II HD to Launcher.exe.
That's it. You should be able to run the game now without interruption. The only downside to this is that, whenever there's an update, you need to repeat this process.