There's an interview video clip that also shows some in-game action.
The new units for the other four races are, I believe,
- Fire Dragons for Eldar
- Chaplain for Space Marines
- Mega-Armoured Nobz for Orks
- Khorne Berzerkers for Chaos
I think they'll also be moving some units around up or down the tech tree, maybe, like maybe make Nob squads early so that Orks have a heavy infantry unit to work with early on and make the mega-armoured ones late-game.
Expected release date is about September 2005, IIRC.
I'm looking forward to this.
