I played the Table Top game for awhile but I haven't tried the PC demo yet. How does it compare?
Well, the game is a straight forward RTS. It's not turn based and incorporates a hero feature much like Warcraft III. The balance of the units in relation to the vehicles is what gets me every time. One tank can actually blow apart a squad.
Unfortunately there were only two skirmish levels and one campaign level so I really can't say how I'd rate this game until I buy it. From what I can tell so far, relic has done a great job of bringing the Space Marines to life.
Try the demo. You might like it.