Here's an honest review.
R:TW is everything Civilization/Age of Empires should have been.
As has been said, the campaign map affects your battles. The terrain, location of your forces, force makeup etc... all affect the battle. I think there are something like 1300 different battle maps you can fight on. The videos are actual ingame footage, the game is so good the History channel is using it to recreate battles.
You control the outcome, and its strategy not build and rush of 'traditional' RTS games. You have the best of both worlds here:
RTS - Control hundreds of men as fighting groups, not annoying individuals. You control their speed, formations, direction, and special abilities like fire arrows, testuga, spread out etc... the list goes on. How you manage your men is all the difference in a battle, not numbers so much as the quality of the troops, the makeup of the army, and the terrain you fight on all affect the outcome. Skill comes first though.
If this isn't your thing, you can do as my Dad is doing. He loves Civ style games but doesn't like RTS. So play on Medium difficulty and let the AI resolve the battles.
Campaign - As they said a micro-managers dream. The AI could be more intuitive and have more options for those players that don't like to micro-manage. All your decisions though affect battle play. Better roads increase trade, hence cash for armies, and increase movement speeds etc... you design your empire. You have assassins, diplomats, spies... how you use them is up to you.
The game can be everything you want, if your interested in strategy games in this time period this game is for you. I've played them all and so far nothing holds a candle to this. Sure it has its downpoints... naval battles, some of the AI decisions are downright annoying, path finding at times such as in the city, but overall they did an excellent job and this game is well worth the ratings its received. And I expect they'll patch the majority of the most glaring bugs, which are few indeed, least on my system.