interested in this myself
To answer my own question, the new DLC works fine with the latest trainer. I think the DLC is worth the asking price of 10$ for what you get.
-new maps-new units, even experimentals for all three factions-new upgradeable powers and additions to the tech trees
I was so happy to see the Cybran Monkey Lord included
All the new content is exclusive to skirmish and multiplayer modes. There is no new single player campaign material.
If you want more detailed info check out the steam page for the new DLC.
[Edited by Mars888, 9/30/2010 2:48:37 AM]