It has a new campaign of 8 scenarios situated in the area of modern day England and Wales, starting from the initial landing of Romans and continuing up to Boudica's rebellion. There are some gameplay related changes (e.g. units have different spotting ranges, making some of the weaker units better scouts) but the overall the gameplay experience is very familiar to veterans of original Populus Romanus.
Naturally the original game will continue to be supported as well. On that front, I'm going to make those Hannibal scenarios harder as requested by several players.