Im a hardcore RTW fan, and i have to reply to Vexator first. The reason people usually wait, is because its easier to defend then to attack, less micro-management. However, Cretean Archers usually get them out of that position, because their range is totally awesome. Also Horse Archers will make them angry.
Lag is a problem, yes, i had lag when i played MTW, and RTW is like using all 3D models, of course lag would be present.
I have beaten the Imperial Campaign with the Julii and Scipii families, a long with Gaul, Egypt, and im working on Parthia at the moment. Note Gaul, Egypt, and Parthia are unlockable factions.
This game is still by far the most realistic game based on Rome out there. If your computer can take it, up the unit size to Huge, making the Legionary Cohorts up to 161 soldiers... Although it is still far off the realistic number of soldiers which would be in a cohort (approximately 500?), it still is VERY realistic, and most likely resembles actual battles very well.