It adds a ton of new planets and units. Doesn't have a very unified theme, but still pretty fun imo. I've only played as the consortium in galactic conquest and if you conquer Mechis III you can build all kinds of CIS units. Like MTTs, which are like AT-ATs that spawn like 100 B1 droids you can use to march in front of everyone else to soak up turbolaser tower fire.
Corellia and Naboo are also inhabited by CorSec and Naboo starfighters in space, so they tend to keep the AI players away.