Thanks for the comments, I'm glad to hear you're enjoying the game.
When we first started the Philip of Macedon game more than 5 years ago we admittedly didn't have the clearest picture in our heads on what kind of game we were making. Being avid strategy gamers we had lots of ideas on what we wanted to include and what we wanted to avoid, but the overall feel of the game didn't really come together until fairly close to release.
However, after spending a lot of time talking to fans at trade shows and in the forums, we had a much stronger feel for what the game was all about when we set out to do Hegemony Gold and I think this stronger vision was affirmed by the pretty much universal approval of the fairly significant changes we made to the balance and gameplay in Gold.
Having locked onto what makes Hegemony cool and unique, our goal with Hegemony Rome was not to redefine the gameplay, but to continue that polish and refinement we started with Gold while applying it from the ground up to all new maps, units, objectives, etc. So, while Rome does have some new features like bridges, supply camps and city upgrades, I'm quite confident players of Hegemony Gold are going to feel right at home.
Regarding the AI: I'll admit the AI in gold is not your traditional wargame AI in that it was originally designed to help play out the Philip campaign rather than to take the place of a human opponent. To stick with the historical scenario, we didn't want, for example, the AI controlled Persian Empire to take over Athens because this would invalidate a lot of the objectives. So we designed the AI to be more reactionary rather than offensive. Unfortunately, these limits became more obvious in Hegemony Gold when we added the sandbox mode and, although I made a few adjustments to try and expand the AI's abilities, more significant improvements were beyond the scope of an expansion. However, for Hegemony Rome we've been planning the sandbox mode from the beginning and so you'll encounter much more traditional wargame AIs that are just as intent on taking over the world as you are.