Since there isn't a big thread already, I figured I'd start one. (Though maybe there just aren't a lot of interested people.)
A few things I notice (Remember that the news about the game has been out for several months now, these are just descriptions from information from that time.):
1. In general it's a rehash of starcraft, with extra types and combinations of abilities added. (Not a criticism or complement from me, it just means that a lot of the big things are the same.)
2. A lot more mobility/raiding units. (reapers, stalkers, vikings, warp in, cliff climbing.)
3. A lot more special attacks and abilities. There are very few units that simply attack with a particular damage type and cooldown, most units either have some trick or oddity to their attacks, or have some sort of special ability.
4. The protoss and terrans seem a bit more differentiated, Terrans get an even larger focus on ranged units and multi-purpose, transforming units, as well as defensive buildings. Protoss get more "expensive, high power" units with unusual attacks. Zerg seem to have gotten more "swarmy" from what has been shown with zerglings and mutalisks, though it is hard to tell since almost no units have been shown. (3 have been directly shown, and it is safe to say drones are in.)
5. The single player character shown talk quite clunkily and cliched, though the idea for how the campaign works is a neat way to do it.
A minor silly side thought:
5. The Thor is pretty much how libertariens stereotypically think of governments, big, expensive, very destructive, and slow to react and turn to face new issues.
The wikipedia page
The web page (Which has some units descriptions under "features".
Terran demonstration video (from around August)
Single player demonstration
the protoss pne from March