It's a great game. A lot of the complaints I've seen from others are true, but they don't bother me. I'd describe the game as a cross between Total War and Starcraft, and that is true in that it has RTS and strategic aspects, but that really doesn't do the game justice. It's just massive. I'm 9 hours into a campaign, and I'm about 25% finished.
Things I love:
1. The realistic complexity: Walking your army through a small area without many farms may very well eat all their food and cause them to revolt. Everything in the game has a cost/benefit, and the game designers clearly went to a great deal of effort to make the game feel authentic.
2. It's addictive: I find myself playing for 5 hours and still wanting to "just finish this one thing".
3. The single player campaign: It basically follows Caesar's accounts of his wars in Gaul. If you've read his memoirs, you know the entire campaign because it pretty much follows it to the letter. I was annoyed with the final fight with Vercingetorix. I was expecting massive attacks from all sides, but there was just a large army sent out from the city which I locked up in a choke point and took out with my archers with zero losses.
4. The seemless transition between the strategic and tactical map. No other game I've played has ever tried this. They've truly pushed the genre on this one. It took a while to get the hang of it, but it works very well. Sometimes, it works too well. Imagine trying to fight 4 "Total War" fights simultaneously. This happens and it can be annoying. On the other hand, this is only happening because I'm pushing 3 armies up through Gaul at the same time while they are also attacking my flank. That's awesome.
Complaints about the game:
1. It's too easy. Granted, I've been playing these games forever, so I'm good, but after your troops get upgraded, they just roflstomp any opponents. This is partly because the computer doesnt attack smartly and partly because the computer upgrades its units stupidly. The computer is, however, persistant, and if you don't cover your flanks, for both your army and your cities, you will be punished. The first hour of a map is difficult with limited resources. After that, I've got so much gold, food, and wood that I don't even bother to optimize my cities.
2. Balance. This is always difficult to do, and I realize that. Getting experience for your archers is a pain, but once fully upgraded, archers with anything in front of them to tank just annihilate any opponent in about 2 seconds. In fact, you really don't need anything tanking for your archers. It's only a little helpful when you're in a 2v10 fight.
3. Crashes. My games crash about once ever 3 hours. However, Total War also crashes about once every 3 hours. I just save a lot.
All in all, I've played for 60 hours and I'm not ready to quit. It's addictive, fun, and interesting.