First of all, I'd like to say that I'm an experienced but not expert player of the Paradox Games. That means that I've played Hearts of Iron III a few years ago (and enjoyed a Communist Greece, amongst my other "achievements") and also love Europa Universalis IV. I saw EU: Rome on Steam and, basically, bought it to give it a try.
1) For a 2008 Game, Graphics should've been better.
2) Not the variety of factions that HoI3 or EUIV have.
3) Steam version forces you to search for the manual here. Also, the tutorial could've been better.
4) Surely, not as worth as EUIV but I'd love to try something until HoI4 goes public.
5) There are no mods is Steam for this game. Maybe the CD version (regular installation) supports them, but I couldn't find anything here.
1) Cheap. 10 euros for a Grand Strategy Game by Paradox. It's God's will!
2) The "Vae Victis" expansion and all patches are included.
3) Historical accuracy and interesting gameplay. It starts with the Invasion of Pyrrhus in Italy and the wars between Romans and Greeks.
4) Variety of historical starts. From an early Roman Republic to the Civil Wars and the foundation of the Roman Empire. Yeah!
5) Awesome music. That may sound stupid, but have a look at YouTube... Yeah, you're welcome.
6) Don't know if it's the way the AI works, but a huge advantage of the game is that factions like Rome, Carthage, Seleucids, Egypt, Macedon and Pontus actually grow up. So, a player gets to experience the "anxiety" of fighting Rome in Magna Graecia or Carthage in Africa. If you're a TWR2 player, you'll see a huge difference. Factions like the Illyrians don't consume Empires in no time, like in Rome 2. You hear that CA?
I don't guarantee that it'll be an unforgetable experience, but it's a nice, fun game to play, balanced enough for its kind.
Have fun! God keep you all safe.