Game is out.
It's a tactical real-time wargame, bordering on strategic (though there's no unit-building BS; it's pure warfare) depending on which level you tackle. You can play as a brigade, division, or corps commander, and the level of command really makes a big difference in the gameplay. The game can support 5,000 units (representing 50,000 men, from a 1:10 ratio). There's a good chain of command system, so that the AI can really support you. You can thus focus on setting up a proper plan rather than fixate over clicking quickly. I'd say the AI is pretty good. I've found it to be pretty realistic, in terms of tactical maneuvers like flanking and so on. There's also a morale and fatigue system that can play a large role.
There are 48 scenarios, IIRC. Units transfer from one scenario to the next. I'm not sure exactly how long each one would be, but judging from what'd I've played so far, I'd say they should be at least about 1 hour long each. Heck, the tutorial battle I had lasted 1h30. In terms of replayability, the devs have made it so that there's always some uncertainty in the scenarios, what with some random variants. For example, an ally may say he's going to support your flank, but end up never showing up (which is what happened historically for that battle). Or sometimes he does. They wanted to create situations where the player would have to get him/herself out of the mess, without having the outcome already predetermined from the start. Pretty neat, if you ask me.
There's also an Open Play mode, where you can customize whole Orders of Battle (that means being able to configure the whole setup for your army/corps). You can set up different goals for the battle, such as Attack, Defend, Objective Points, etc. Couriers add a nice dynamic layer to it, in that you can receive orders from other generals that ask you, for example, to secure a particular location (AI-directed commands, not pre-scripted). Likewise, you can do the same (sending couriers to others).
I'd say the demo is fairly representative of the game. It features two tutorials and one scenario. The tutorials allow you to control a brigade (which consist of a couple of regiment, eg. a few hundred men), and a division (which is a couple of brigades). A corps consists of a couple of divisions, but it's not available in the demo. The nice thing about the maps is that they're HUGE. Even when you command a whole corps (which, when you add things up, amounts to a LOT of troops), you'll have AI generals fighting alongside you. It really makes you feel part of a massive battle. When you see your allied flank break off and rout, you know you're in trouble
I suggest you read some more reviews/previews from http://madminutegames.com/ (check the left side). It's generally very positive (main gripes would be that it's too slow-paced, and requires patience, as opposed to conventional twitch-fest RTS; but then, which one has actual strategy/tactics?). In fact, the game's predecessor won 'Wargame of the year' last year at http://www.wargamer.com
Just try out the demo and see for yourself. That's what sealed the deal for me.
From the screenshot thread, the aftermath of 90 min of fighting.