Were you expecting this?
I love competitive games, CSS, TF2, etc. I always get into games that require skill, I think what attracts me is that the more I play the more I can smack talk and own noobs. The sort of gameplay Starcraft offers sounds just like that, fast-paced and skillful.
Starcraft 2 has three different races; Terran, Protoss and Zerg just like Starcraft 1. When I say different races I mean it, the fundemental idea of Starcraft is that the 3 races should be as unique as possible.
Here's the new Zerg unit the infestor:
While it doesn't look like much in that shot he's deadly in the game. It can burrow silently into position before infecting a building or unit. Infected units will spread disease to anyone around them, infected buildings produce slow and also infected units.
One of the new things in SC2 is how the Single Player Campaign works. Once you complete a mission you go to the headquaters area of the race you're fighting with. And the game turns into a point and click adventure game. You interact with main characters and can progress through the campaign in a Non-Linear way. Sounds pretty awesome to me.