a few hours to kill

Aliens.

Starcraft II doesn't seem that different from the first one yet (haven't tried MP yet). Units die fast, like I remember from the first one. There's a little bit of rock-paper-scissors on the units, but that was there before because of the shields on one side and the swarm strategy on the other. The campaign is different because of the way upgrades are handled (and more of them) and having mercs to draw on, but I don't see much difference yet other than graphics that should have taken over a decade to make sequel for the original...much less that they'll need to release the 3 campaigns as 3 separate games.

Back to the grind though. Play with it some more when there's less on the plate.