okay, after a little while with the demo i have some impressions...
the controls work pretty well. the game is relatively "streamlined", so doesn't require nearly the same level of micromanagement that something such as generals, for example, would. if it did, you'd be screwed, but in the context of this game, the control scheme is very well designed. you've got a decent array of commands, giving you a good level of control on the battlefield. you can select individual units, all units of the same type on screen, all units on map, or all the units on screen. the individual selection marker works well too - the longer you hold the button down, the more it grows - enabling you to select a group of units in the same vicinity. obviously, you're not able to use some common rts commands, such as control grouping, map markers, etc - and that does make it feel slightly restrictive, but "slightly" really is the operative word.
the base building is limited. it's functional, but there are few options. it's not a terrible design choice, but i think that ensemble could of afforded to be a little bolder in depth without over complicating things too much. the focus is more on research. pretty much every unit and structure can be upgraded several times, making them much more useful than their starting versions (a lot like dawn of war).
the demo campaign missions are quite fun - you can't do a hell of a lot, because like most rts games, the tech is introduced slowly throughout the campaign. the cut scenes are superb though, if you are at all interested in the halo universe, you'll definitely get a kick out of these. as for the skirmish mode, that shows off a whole lot more of the full product. you only have the one map, but you can use every unit and structure (from what i gather) - and it's great fun!
being a long time pc rts nut, i was fully ready to hate this - i couldn't fathom how a pad could possibly work - but it does, and the game itself looks to be genuinely good. i didn't think it would happen, but i think i may well end up buying this game.