Every time I start this game, time just flies, and I spend another 3+ hours just for the glory of the roman empire.
It's a relaxing, fun game, and it works pretty well, once you figure out how buildings and settlers depend on each other.
For example: Temples and altars are important. Make sure most houses have one in their radius (which shows when you click on buildings).
Also make sure to have enough slaves, especially if you start selling goods.
You need a lot of them, otherwise they slow down every progress!
I played 6 long missions so far, and the game just crashed a single time, even though I listen to Alex Jones Radio show (Infowars.com) online via Winamp, and had lots of background programs running.
I also like to play Total War and many other games, but I often switch to Imperium Romanum in between, because it provides a nice, enjoyable, challenging, and fun time.