The demo of Microsoft's and Ensemble Studios' Halo Wars is not due to hit the Marketplace until next week, but thanks to the XCN we got access to it a week early. It includes two maps, tutorial and a skirmish mode. I captured the two maps and the (previously shown) intro, while I'll let you see the other two CG movies by yourself when you play the demo!
The pace in the demo is really high, you basically build up your base and then advance through waves of enemies. I don't know if this is the case later on in the game, but I was positively surprised to see how much action is involved here. The graphics serves its purpose with a clear image while the framerate goes down a bit at certain points, mainly around your own base.
Regarding the controls, you can choose between selecting all units on screen, all units on battlefield, units within a certain radius and single units. When attacking you can do basic attack with X or the special attack on Y: scout warthogs rams over enemies, while marines throws grenades (which can be upgraded). Some buttons have an announcement tied to them, meaning you will have to get used to hearing "All units" very often on the battlefield.
Now enjoy these three videos, showing the intro, the first short level and the longer second level. I took the liberty to capture a couple of images from the cut out CG sequences.