I was playing the demo of Company of Heroes today and thinking, "This is absolutely great. They took everything fun about Warhammer 40K: Dawn of War and somehow managed to both extend it and yet keep it just as intuitive. I must get the full game."
I don't often feel that way playing demos. I actually had a blast just playing the tutorial.
According to Flash of Steel, this seems to be the consensus.
If I were to describe it, I'd tell you to think of all those things that true-blue grognards seem to love - arcs of fire, armor thickness, supply lines, suppression - and then imagine them integrated into an easily-accessible, clearly-understood game.
Dawn of War was similar, in that small tactical changes could have actual consequences, and I'd love to hear that the new expansion would incorporate the new concepts explored in Heroes.
With Blizzard too busy trying to please the hungry ghosts (MMO-players) to bother making a Starcraft sequel, it looks like THQ/Relic is taking over the RTS throne.